javascript get current function name in strict mode

How to print and connect to printer using flutter desktop via usb? Note: In function calls like f(), this value was the global object. Making statements based on opinion; back them up with references or personal experience. const {stack} = obj; Those s*****s are not happy enough complexing their stuff, they have to limit other's software. How to get file input by selected file name without path using jQuery ? arguments.callee for strict mode functions is a non-deletable property which throws an error when set or retrieved: Reserved words are identifiers that can't be used as variable names. So "use strict"; only matters to new compilers that "understand" the meaning This is to prevent code from being able to "walk the stack", which both poses security risks and severely limits the possibility of optimizations like inlining and tail-call optimization. You may have to parse the name though, as it will probably include some extra junk. Javascript: is the arguments array deprecated? Whereas in strict mode, the JavaScript sets this to undefined mode. JavaScript used to silently fail in contexts where what was done should be an error. rev2023.4.21.43403. Using Strict mode for the entire script: To invoke strict mode for an entire script, put the exact statement use strict; (or use strict;) before any other statements. Until ES2015, there was no standard way to get the name of a function. Try it. Print the content of a div element using JavaScript, JQuery | Set the value of an input text field. How to combine several legends in one frame? Strict Mode was a new feature in ECMAScript 5 that allows you to place a program, or a function, in a strict operating context. Parabolic, suborbital and ballistic trajectories all follow elliptic paths. Note that the only behavior specified by the ECMAScript specification is that Function.prototype has an initial caller accessor that unconditionally throws a TypeError for any get or set request (known as a "poison pill accessor"), and that implementations are not allowed to change this semantic for any function except non-strict plain functions, in which case it must not have the value of a strict mode function. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. For example I got a function like, I have it in my head section. How to change selected value of a drop-down list using jQuery? This is also why things like the name attribute on form fields or expressions like 'form.myField.value' still work. Use of reserved keywords as variable or function name. The value passed as this to a function in strict mode is not forced into being an object (a.k.a. Create function: After that whenever you need, you simply use: Warning: The 5th edition of ECMAScript (ES5) forbids use of arguments.callee() in strict mode. But arguments.callee.name only works in loose mode. When adding 'use strict';, the following cases will throw a SyntaxError before the script is executing: These errors are good, because they reveal plain errors or bad practices. If (like me) you want to define this elsewhere and call it generically, you can store the code as a string somewhere global or import it, then eval() it wherever to access the current function name. That way I can shown an error and know in which function the error happened without hardcoding the function's name, get the current function name in javascript. are on the stack, but it will include the value of each argument that Critical issues have been reported with the following SDK versions: com.google.android.gms:play-services-safetynet:17.0.0, Flutter Dart - get localized country name from country code, navigatorState is null when using pushNamed Navigation onGenerateRoutes of GetMaterialPage, Android Sdk manager not found- Flutter doctor error, Flutter Laravel Push Notification without using any third party like(firebase,onesignal..etc), How to change the color of ElevatedButton when entering text in TextField. Those previous arguments remain available through arguments, so they're not completely inaccessible. How about saving the world? It's Block Surface; It canned becoming assigned go the changeable on the declaration border. 2. arguments[i] does not track the value of the corresponding named argument, nor does a named argument track the value in the corresponding arguments[i]. Clone with Git or checkout with SVN using the repositorys web address. This is exactly what I was looking for without instantiating a new Error (although it still parses a call stack). Still, this hiding makes little sense and is probably undesirable (it might hide a typo, for example), so in strict mode, duplicate argument names are a syntax error: Strict mode forbids a 0-prefixed octal literal or octal escape sequence. In sloppy mode, eval("var x;") introduces a variable x into the surrounding function or the global scope. How to count number of notification on an icon? JavaScript's flexibility makes it effectively impossible to do this without many runtime checks. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. ?` unparenthesized within `||` and `&&` expressions, SyntaxError: continue must be inside loop, SyntaxError: for-in loop head declarations may not have initializers, SyntaxError: function statement requires a name, SyntaxError: identifier starts immediately after numeric literal, SyntaxError: invalid assignment left-hand side, SyntaxError: invalid regular expression flag "x", SyntaxError: missing ) after argument list, SyntaxError: missing ] after element list, SyntaxError: missing } after function body, SyntaxError: missing } after property list, SyntaxError: missing = in const declaration, SyntaxError: missing name after . A simple solution to dynamically retrieve function names [like magic variables] is the use of scoped variables, and the Function.name property. Can I get the name of the currently running function in JavaScript? If the function f was invoked by the top-level code, the value of f.caller is null; otherwise it's the function that called f. If the function that called f is a strict mode function, the value of f.caller is also null. It can be applied to individual functions. How a top-ranked engineering school reimagined CS curriculum (Ep. Difference between var and let in JavaScript, Convert a string to an integer in JavaScript. It can be applied to individual functions. Strict mode prohibits some syntax likely to be defined in future versions of ECMAScript. This page was last modified on Apr 5, 2023 by MDN contributors. How to get the class of a element which has fired an event using JavaScript/JQuery? How to get the function name from within that function? Just call console.trace() and Firebug will write a very informative rev2023.4.21.43403. In sloppy mode, function calls like f() would pass the global object as the this value. Some websites now provide ways for users to write JavaScript which will be run by the website on behalf of other users. Javascript: How can I get the name of a function? I hadn't thought of that. How to pop an alert message box using PHP ? How to change the style of alert box using CSS ? But arguments.callee.name only works in loose mode. are deprecated, SyntaxError: "use strict" not allowed in function with non-simple parameters, SyntaxError: "x" is a reserved identifier, SyntaxError: a declaration in the head of a for-of loop can't have an initializer, SyntaxError: applying the 'delete' operator to an unqualified name is deprecated, SyntaxError: await is only valid in async functions, async generators and modules, SyntaxError: cannot use `? "use strict" is just a string, so IE 9 will not throw an error even if it does not understand it. How do I make function decorators and chain them together? The entire contents of JavaScript modules are automatically in strict mode, with no statement needed to initiate it. Note: Sometimes you'll see the default, non-strict mode referred to as sloppy mode. This isn't an official term, but be aware of it, just in case. It is thus recommended that you enable strict mode on a function-by-function basis (at least during the transition period). Actually, actually paying more attention to your question, it sounds like you might want the extra junk :), This worked for me but I think there's a typo in your regexp. It's possible that a test suite doesn't catch this kind of subtle difference. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, I must be missing something. var functionName = function() {} vs function functionName() {}. Flutter change focus color and icon color but not works. See ; non-standard and not allowed in strict mode, developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/. All parts of a class's body are strict mode code, including both class declarations and class expressions. Only concatenating strict and non-strict scripts is problematic. The property of ampere const object can be changed but e cannot shall changed to ampere reference on to recent object The actual behavior of the caller property, if it's anything other than throwing an error, is implementation-defined. Copy and paste console.debug (arguments.callee) is more convenient ( I do not need to repeat function name). const newStack = stack.split("\n").slice(NUMBER).join("\n"); That's when JS does not have native constants like PHP does with Magic constants @AndyE probably no one pointed it out because once we see a regexp, we enter TL;DR mode and look for other answers ;), Works perfect even for arrow functions, underrated answer. Has the cause of a rocket failure ever been mis-identified, such that another launch failed due to the same problem? Content Discovery initiative April 13 update: Related questions using a Review our technical responses for the 2023 Developer Survey. this.timer = setTimeout (function () { self.clearBoard (); // Oh, OK, I do know who 'self' is! More formally, it's disallowed to have \ followed by any decimal digit other than 0, or \0 followed by a decimal digit; for example \9 and \07. The caller accessor property of Function instances returns the function that invoked this function. Logging and debugging have different use and often logging is more productive over the time (. Was Stephen Hawking's explanation of Hawking Radiation in "A Brief History of Time" not entirely accurate? They occur before the code is running, so they are easily discoverable as long as the code gets parsed by the runtime. JSLint is suddenly reporting: Use the function form of "use strict". In sloppy mode, modifying a value in the arguments object modifies the corresponding named argument. The fact that you want the function name is probably a good indication that you're thinking about the problem incorrectly. Connect and share knowledge within a single location that is structured and easy to search. 14. arguments.callee. This is just awesome! Also, to get only the name of the function, you need to use arguments.callee.name. Why typically people don't use biases in attention mechanism? var functionName = function() {} vs function functionName() {}. Looking for job perks? How to get the function name under "use strict"? assignment to a non-writable data property, assignment to a getter-only accessor property, Declaring two function parameters with the same name, Declaring the same property name twice in an object literal, Assigning to an undeclared variable throws a, Failing to assign to an object's property (e.g. If you want to report an error, or if you want to make a suggestion, do not hesitate to send us an e-mail: x = 3.14; // This will not cause an error. Both involve a considerable amount of magical behavior in sloppy mode: eval to add or remove bindings and to change binding values, and arguments syncing named arguments with its indexed properties. Adding EV Charger (100A) in secondary panel (100A) fed off main (200A). eval code, Function code, event handler attributes, strings passed to setTimeout(), and related functions are either function bodies or entire scripts, and invoking strict mode in them works as expected. Be aware that this feature may cease to work at any time. Find centralized, trusted content and collaborate around the technologies you use most. In strict mode, eval does not introduce new variables into the surrounding scope. The execution context is not the global object anymore, contrary to above case 2.1. operator, SyntaxError: redeclaration of formal parameter "x". In sloppy mode, arguments.callee refers to the enclosing function. If it's dynamic, you're already accessing it by name, or no? You need something like this if you want the arguments of MyFunction(): You can't do better than reliably, since that function has almost nothing to do with the error handler: The error handler can very possibly have been created in another context entirely, one enclosing MyFunction, or passed into it etc. In strict mode, eval creates variables only for the code being evaluated, so eval can't affect whether a name refers to an outer variable or some local variable: Whether the string passed to eval() is evaluated in strict mode depends on how eval() is invoked (direct eval or indirect eval). Note that you shouldn't do this if you intend to use a minifier like Terser, which may change the function names. Is there a generic term for these trajectories? For strict, arrow, async, and generator functions, accessing the caller property throws a TypeError. Asking for help, clarification, or responding to other answers. How to calculate the number of days between two dates in JavaScript ? Method Invocation global variable. Interpreting non-statistically significant results: Do we have "no evidence" or "insufficient evidence" to reject the null? Knowing the name of the current function can be essential if that function is being created dynamically from a database and needs context information inside the function that is keyed to the function name. Unfortunately, the implementations' semantics diverged, and it became impossible for the language specification to reconcile all implementations. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Careful review of your code base will probably be necessary to be sure these differences don't affect the semantics of your code. Used in global scope for the entire script. In older versions of JS you can get it by using arguments.callee.. You may have to parse out the name though, as it will probably include some extra junk. It's surprising nobody else has pointed that out in the almost 3 years this answer has been here :-). Using a global variable in this case provides you a workaround to this problem. Enable strict mode globally by adding the string "use strict" as the first statement in your file. You cannot deprecate/obsolete/kill that which is actively used all over the web. was passed to each function. Non-standard: This feature is non-standard and is not on a standards track. Is there a weapon that has the heavy property and the finesse property (or could this be obtained)? A-143, 9th Floor, Sovereign Corporate Tower, We use cookies to ensure you have the best browsing experience on our website. How to Open URL in New Tab using JavaScript ? Function.prototype.caller is also not allowed in strict mode. The entire concatenation looks strict, the inverse is also true. Making statements based on opinion; back them up with references or personal experience. Why is it shorter than a normal address? How to get variable name in annonymous function construnction var f = function(){}; How do I remove a property from a JavaScript object? Thanks for contributing an answer to Stack Overflow! "caller is an own property with descriptor", "f doesn't have an own property named caller. after: How a top-ranked engineering school reimagined CS curriculum (Ep. Why doesnt a Javascript return statement work when the return value is on a new line. We use cookies to personalise content and ads, to provide social media features and to analyse our traffic. This is the same answer you got before, just wrapped up in a nice module, and using some V8-specific APIs. If fun is in strict mode, both fun.caller and fun.arguments are non-deletable properties which throw when set or retrieved: Similarly, arguments.callee is no longer supported. These differences are very subtle differences. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Is there any way, in javascript, to obtain the name of the function, inside the function which was called, javascript - Get name of function through a function, How to compare a function when the function is created as the result of another function. You would have to make sure you add that function name twice. Assignments which would accidentally create global variables throw an error in strict mode: Strict mode makes assignments which would otherwise silently fail to throw an exception. For those frames, getFunction() will return undefined. of it. Generic Doubly-Linked-Lists C implementation. Beginner kit improvement advice - which lens should I consider? How is white allowed to castle 0-0-0 in this position? I was just wondering why, FYI function.name is "part of the ECMAScript 2015 (ES6) standard", so it should be future proof (but may not work everywhere today). I would like to have a rudimentary debugging function like this (with npmlog defining log.debug ): 6 1 function debug() { 2 var callee, line; 3 /* MAGIC */ 4 log.debug(callee + ":" + line, arguments) 5 } 6 When called from another function it would be something like this: Can I general this code to draw a regular polyhedron? Strict mode has been designed so that the transition to it can be made gradually. How to create a virtual ISO file from /dev/sr0. Can I get the name of the currently running function in JavaScript. Strict mode isn't just a subset: it intentionally has different semantics from normal code. Hide elements in HTML using display property. This is a good part of the language being strict about throwing errors: it leaves room for future semantic changes. As noted this applies only if your script uses "strict mode". Using "use strict" in functions with rest, default, or destructured parameters is a syntax error. In sloppy mode, a number beginning with a 0, such as 0644, is interpreted as an octal number (0644 === 420), if all digits are smaller than 8. Many compiler optimizations rely on the ability to say that variable X is stored in that location: this is critical to fully optimizing JavaScript code. This means that, in general, in a function containing a call to eval, every name not referring to an argument or local variable must be mapped to a particular definition at runtime (because that eval might have introduced a new variable that would hide the outer variable). It does not change any validation results, but it makes some schemas invalid that would be otherwise valid according to JSON Schema . In strict mode, it is now undefined. You can use strict mode in all your programs. Where NUMBER is the amount of jumps you want to do to the past (Number = 1 => first parent) All modern browsers support "use strict" except Internet Explorer 9 and lower: The numbers in the table specify the first browser version that fully supports the directive. The following code checks the value a function's caller property. Consider: At the moment stop() is called the call stack will be: so if you tried to get the stack trace in the stop() function like this: If the caller is a strict mode function, the value of caller is null. Strict mode simplifies how variable names map to particular variable definitions in the code. Strict mode makes several changes to normal JavaScript semantics: Strict mode applies to entire scripts or to individual functions. Great job. How to execute a JavaScript function when I have its name as a string. Both extensions are problematic for "secure" JavaScript because they allow "secured" code to access "privileged" functions and their (potentially unsecured) arguments. older versions of JavaScript. Do you think it is possible also to get the parent function's name? How to get currently running function name using JavaScript ? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. We address our most frequently seen support requests here, so it is a great place to check for solutions to any issues you may have. JavaScript : Can I get the name of the currently running function in JavaScript? JavaScript was designed to be easy for novice developers, and sometimes it gives operations which should be errors non-error semantics. This is why W3C's attempts to deprecate tags like and has failed. Beginner kit improvement advice - which lens should I consider? What is the scope of variables in JavaScript? Fixes mistakes that make it difficult for JavaScript engines to perform optimizations: strict mode code can sometimes be made to run faster than identical code that's not strict mode. Solution 1. The "use strict" directive can only be applied to the body of functions with simple parameters. Note: Using Function.caller is non-standard and arguments.callee is forbidden in strict mode. Why Is PNG file with Drop Shadow in Flutter Web App Grainy? Here's what I use to put class names in error messages. Creating Error object for each calling is just a hack, not a working method. All what you need is simple. For example, Chrome defines it as an own data property, while Firefox and Safari extend the initial poison-pill Function.prototype.caller accessor to specially handle this values that are non-strict functions. Here's what happens when you use code based on it: You'll then be able to reference obj1.func.name and it'll return 'test1'. In strict mode, this is a syntax error. Or will it be in future plans ECMA6, 7? W3Schools is optimized for learning and training. Time to refresh this thread by a fresh answer :). In strict mode you can no longer reference callee (see the related discussion at Javascript: is the arguments array deprecated?) Given a function and the task is to get the name of function that is currently running using JavaScript. Is there any new proper (standard) alternative for getting function name inside actual function? Which ability is most related to insanity: Wisdom, Charisma, Constitution, or Intelligence? webpack: Module not found: Error: Cant resolve (with relative path). In strict mode, this will throw an error, making it impossible How to add options to a select element using jQuery? Which function is used to prevent code running before document loading in jQuery ? stacktracey seems to work cross browser pretty well. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Thanks for contributing an answer to Stack Overflow! In my case, it had to do with mocking and spying during tests. The problem is that what works in today's browser may not work in tomorrow's. In strict mode, it is now undefined. In sloppy mode, mistyping a variable in an assignment creates a new property on the global object and continues to "work". ES6 class methods. How to find all inputs that don't have color name and appends text to the span next to it using jQuery ? How can one get the name and line of a function that called the current one? If you want to get name from outside you may parse it out of: but I think name property of function object might be what you need: this however does not seem work for IE and Opera so you are left with parsing it out manually in those browsers. How do I get the current date in JavaScript? What woodwind & brass instruments are most air efficient? JavaScript: How to get the caller (parent) function's name I recently had the need to find out the name of the function that was invoking another specific function in a NodeJS code base. Share Improve this answer Follow edited Dec 26, 2013 at 15:03 answered Jul 5, 2011 at 18:18 MD Sayem Ahmed 28.5k 27 111 178 Add a comment 6 Set a default parameter value for a JavaScript function. In strict mode, it is now undefined. arguments objects for strict mode functions store the original arguments when the function was invoked. Attempts to delete a non-configurable or otherwise undeletable (e.g. It is possible to change each file individually and even to transition code to strict mode down to the function granularity. Note: Nested functions cease to be source elements, and are hence not hoisted. What does the power set mean in the construction of Von Neumann universe? Therefore, block-scoped function declarations are only explicitly specified in strict mode (whereas they were once disallowed in strict mode), while sloppy mode behavior remains divergent among browsers. Using Strict mode for a function: Likewise, to invoke strict mode for a function, put the exact statement use strict; (or use strict;) in the functions body before any other statements. When a function was called with call or apply, if the value was a primitive value, this one was boxed into an object (or the global object for undefined and null). }, 0); }; Alternatively, in newer browsers, you can use the bind () method to pass in the proper reference: In strict mode, the arguments object is created and initialized with the same values than the named arguments, but changes to either the arguments object or the named arguments aren't reflected in one another. There are two ways to use it: In global scope: Use Strict Mode for the entire script. There are some chances is not even working there. are not allow to access their receiver and function objects. Making statements based on opinion; back them up with references or personal experience. I had to take out the backslash before the, @declan: yep, you're right. In strict mode, any assignment to a non-writable property, a getter-only exebook For logging/debugging purposes, you can create a new Error object in the logger and inspect its .stack property, e.g. So for other coming here the answer is YES and you can just add this line: Using the function.caller Property In this approach, we will use the function.caller property in JavaScript. It simply compiles to a non existing It includes code to get the name of functions, which works in most browsers. This page was last modified on Apr 12, 2023 by MDN contributors. Looking for job perks? Download ZIP [NodeJS] Get the current function name or any other function while using strict mode Raw functionName.js 'use strict'; const findFirstOccurrence = (string, searchElements, fromIndex = 0) => { let min = string.length; for (let i = 0; i < searchElements.length; i += 1) { const occ = string.indexOf (searchElements [i], fromIndex); You might want to post a new question where you can illustrate your, This is not exactly a "proper" way, so I am not posting it as an answer, bit it might be good enough for debugging. mode will return the global object (window): Keywords reserved for future JavaScript versions can NOT be used as variable Moreover, arguments.callee substantially hinders optimizations like inlining functions, because it must be made possible to provide a reference to the un-inlined function if arguments.callee is accessed. *only with JSON Schema ** only with JSON Type Definition # Strict mode options v7 # strict By default Ajv executes in strict mode, that is designed to prevent any unexpected behaviours or silently ignored mistakes in schemas (see Strict Mode for more details). Strict mode makes it easier to write "secure" JavaScript. Why typically people don't use biases in attention mechanism? In ES5 and above, there is no access to that information. To learn more, see our tips on writing great answers. I've moved code around and forgotten to update the hard-coded function names. Strict mode reserves some more names than sloppy mode, some of which are already used in the language, and some of which are reserved for the future to make future syntax extensions easier to implement. In function calls like f(), this value was the global object. Is there any new proper(standard) alternative for getting function name inside actual function? In normal code arguments.callee refers to the enclosing function. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. inspect them further. Learn more about bidirectional Unicode characters. Can you still use Commanders Strike if the only attack available to forego is an attack against an ally?