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function main()
{
   Hello();
}

function Hello()
{
  // How do you find out the caller function is 'main'?
}

Is there a way to find out the call stack?

function main()
{
   Hello();
}

function Hello()
{
  // How do you find out the caller function is 'main'?
}

Is there a way to find out the call stack?

• javascript
• callstack

Share Improve this question Follow edited Mar 23, 2019 at 4:04 Hearen 7,80844 gold badges5757 silver badges7373 bronze badges asked Nov 11, 2008 at 9:04 Ray LuRay Lu 26.6k1212 gold badges6262 silver badges5959 bronze badges 13

• 79 I hope this is just to aid you in debugging. Varying behaviour based on the caller is a bad idea. – OJ. Commented Nov 11, 2008 at 9:15
• 38 @AndersonGreen when you've got, for example, a default template render method and see it's being called twice. Rather than combing through 1000s of LoC or arduous stepping through with the debugger, you can just see what was the stack at the time. – tkone Commented Oct 20, 2012 at 19:04
• 32 to see the stack trace use console.trace() for chrome. don't know about others though – lukas.pukenis Commented Oct 10, 2013 at 17:36
• 16 Why is this a bad idea? – J-Cake Commented Jul 28, 2019 at 9:36
• 19 "I hope this is just to aid you in debugging. Varying behaviour based on the caller is a bad idea." Why we should be able to downvote comments. He didn't ask if it was a good idea, and you're also wrong. It's immensely useful in other languages like C# when you want to notify subscribers of a property change without magic strings that don't refactor easily. – Emperor Eto Commented Apr 25, 2021 at 14:25

 |  Show 8 more comments

38 Answers 38

Sorted by: Reset to default 1 2 Next 1080

Note that this solution is deprecated and should no longer be used according to MDN documentation

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/caller

---

function Hello()
{
    alert("caller is " + Hello.caller);
}

Note that this feature is non-standard, from Function.caller:

Non-standard
This feature is non-standard and is not on a standards track. Do not use it on production sites facing the Web: it will not work for every user. There may also be large incompatibilities between implementations and the behavior may change in the future.

---

The following is the old answer from 2008, which is no longer supported in modern Javascript:

function Hello()
{
    alert("caller is " + arguments.callee.caller.toString());
}

StackTrace

You can find the entire stack trace using browser specific code. The good thing is someone already made it; here is the project code on GitHub.

But not all the news is good:

1. It is really slow to get the stack trace so be careful (read this for more).

2. You will need to define function names for the stack trace to be legible. Because if you have code like this:

   var Klass = function kls() {
      this.Hello = function() { alert(printStackTrace().join('\n\n')); };
   }
   new Klass().Hello();
   

   Google Chrome will alert ... kls.Hello ( ... but most browsers will expect a function name just after the keyword function and will treat it as an anonymous function. An not even Chrome will be able to use the Klass name if you don't give the name kls to the function.

   And by the way, you can pass to the function printStackTrace the option {guess: true} but I didn't find any real improvement by doing that.

3. Not all browsers give you the same information. That is, parameters, code column, etc.

---

Caller Function Name

By the way, if you only want the name of the caller function (in most browsers, but not IE) you can use:

arguments.callee.caller.name

But note that this name will be the one after the function keyword. I found no way (even on Google Chrome) to get more than that without getting the code of the whole function.

---

Caller Function Code

And summarizing the rest of the best answers (by Pablo Cabrera, nourdine, and Greg Hewgill). The only cross-browser and really safe thing you can use is:

arguments.callee.caller.toString();

Which will show the code of the caller function. Sadly, that is not enough for me, and that is why I give you tips for the StackTrace and the caller function Name (although they are not cross-browser).

I usually use (new Error()).stack in Chrome. The nice thing is that this also gives you the line numbers where the caller called the function. The downside is that it limits the length of the stack to 10, which is why I came to this page in the first place.

(I'm using this to collect callstacks in a low-level constructor during execution, to view and debug later, so setting a breakpoint isn't of use since it will be hit thousands of times)

In both ES6 and Strict mode, use the following to get the Caller function

console.log((new Error()).stack?.split("\n")[2]?.trim().split(" ")[1])

Please note that, the above line will throw an exception if there is no caller or no previous stack. Use accordingly.

To get callee (the current function name), use:

console.log((new Error()).stack?.split("\n")[1]?.trim().split(" ")[1]) 

I know you mentioned "in Javascript", but if the purpose is debugging, I think it's easier to just use your browser's developer tools. This is how it looks in Chrome: Just drop the debugger where you want to investigate the stack.

If you are not going to run it in IE < 11 then console.trace() would suit.

function main() {
    Hello();
}

function Hello() {
    console.trace()
}

main()
// Hello @ VM261:9
// main @ VM261:4

You can get the full stacktrace:

arguments.callee.caller
arguments.callee.caller.caller
arguments.callee.caller.caller.caller

Until caller is null.

Note: it cause an infinite loop on recursive functions.

To recap (and make it clearer) ...

this code:

function Hello() {
    alert("caller is " + arguments.callee.caller.toString());
}

is equivalent to this:

function Hello() {
    alert("caller is " + Hello.caller.toString());
}

Clearly the first bit is more portable, since you can change the name of the function, say from "Hello" to "Ciao", and still get the whole thing to work.

In the latter, in case you decide to refactor the name of the invoked function (Hello), you would have to change all its occurrences :(

I would do this:

function Hello() {
  console.trace();
}

You can use Function.Caller to get the calling function. The old method using argument.caller is considered obsolete.

The following code illustrates its use:

function Hello() { return Hello.caller;}

Hello2 = function NamedFunc() { return NamedFunc.caller; };

function main()
{
   Hello();  //both return main()
   Hello2();
}

Notes about obsolete argument.caller: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/arguments/caller

Be aware Function.caller is non-standard: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/caller

heystewart's answer and JiarongWu's answer both mentioned that the Error object has access to the stack.

Here's an example:

function main() {
  Hello();
}

function Hello() {
  try {
    throw new Error();
  } catch  (err) {
    let stack = err.stack;
    // N.B. stack === "Error\n  at Hello ...\n  at main ... \n...."
    let m = stack.match(/.*?Hello.*?\n(.*?)\n/);
    if (m) {
      let caller_name = m[1];
      console.log("Caller is:", caller_name);
    }
  }
}

main();

Different browsers shows the stack in different string formats:

Safari  : Caller is: main@https://stacksnippets.net/js:14:8
Firefox : Caller is: main@https://stacksnippets.net/js:14:3
Chrome  : Caller is:     at main (https://stacksnippets.net/js:14:3)
IE Edge : Caller is:    at main (https://stacksnippets.net/js:14:3)
IE      : Caller is:    at main (https://stacksnippets.net/js:14:3)

Most browsers will set the stack with var stack = (new Error()).stack. In Internet Explorer the stack will be undefined - you have to throw a real exception to retrieve the stack.

Conclusion: It's possible to determine "main" is the caller to "Hello" using the stack in the Error object. In fact it will work in cases where the callee / caller approach doesn't work. It will also show you context, i.e. source file and line number. However effort is required to make the solution cross platform.

Looks like this is quite a solved question but I recently found out that callee is not allowed in 'strict mode' so for my own use I wrote a class that will get the path from where it is called. It's part of a small helper lib and if you want to use the code standalone change the offset used to return the stack trace of the caller (use 1 instead of 2)

function ScriptPath() {
  var scriptPath = '';
  try {
    //Throw an error to generate a stack trace
    throw new Error();
  }
  catch(e) {
    //Split the stack trace into each line
    var stackLines = e.stack.split('\n');
    var callerIndex = 0;
    //Now walk though each line until we find a path reference
    for(var i in stackLines){
      if(!stackLines[i].match(/http[s]?:\/\//)) continue;
      //We skipped all the lines with out an http so we now have a script reference
      //This one is the class constructor, the next is the getScriptPath() call
      //The one after that is the user code requesting the path info (so offset by 2)
      callerIndex = Number(i) + 2;
      break;
    }
    //Now parse the string for each section we want to return
    pathParts = stackLines[callerIndex].match(/((http[s]?:\/\/.+\/)([^\/]+\.js)):/);
  }

  this.fullPath = function() {
    return pathParts[1];
  };

  this.path = function() {
    return pathParts[2];
  };

  this.file = function() {
    return pathParts[3];
  };

  this.fileNoExt = function() {
    var parts = this.file().split('.');
    parts.length = parts.length != 1 ? parts.length - 1 : 1;
    return parts.join('.');
  };
}

function Hello() {
    alert(Hello.caller);
}

It's safer to use *arguments.callee.caller since arguments.caller is deprecated...

2018 Update

caller is forbidden in strict mode. Here is an alternative using the (non-standard) Error stack.

The following function seems to do the job in Firefox 52 and Chrome 61-71 though its implementation makes a lot of assumptions about the logging format of the two browsers and should be used with caution, given that it throws an exception and possibly executes two regex matchings before being done.

'use strict';
const fnNameMatcher = /([^(]+)@|at ([^(]+) \(/;

function fnName(str) {
  const regexResult = fnNameMatcher.exec(str);
  return regexResult[1] || regexResult[2];
}

function log(...messages) {
  const logLines = (new Error().stack).split('\n');
  const callerName = fnName(logLines[1]);

  if (callerName !== null) {
    if (callerName !== 'log') {
      console.log(callerName, 'called log with:', ...messages);
    } else {
      console.log(fnName(logLines[2]), 'called log with:', ...messages);
    }
  } else {
    console.log(...messages);
  }
}

function foo() {
  log('hi', 'there');
}

(function main() {
  foo();
}());

Just console log your error stack. You can then know how are you being called

const hello = () => {
  console.log(new Error('I was called').stack)
}

const sello = () => {
  hello()
}

sello()

Try accessing this:

arguments.callee.caller.name

Using Error.stack property is the general solution for pure javascript for getting a caller function name (or full callstack). But it can be resource intensive in case of long stacks or frequent calls, because you operate with string object by slow trim, split or match methods.

The better solution is accessing to the stack's array of CallSite items directly with prepareStackTrace:

function getCallerName() {
  // Get stack array
  const orig = Error.prepareStackTrace;
  Error.prepareStackTrace = (error, stack) => stack;
  const { stack } = new Error();
  Error.prepareStackTrace = orig;
  
  const caller = stack[2];
  return caller ? caller.getFunctionName() : undefined;
}

It works great with classes, arrow and async functions etc., for instance:

function hello() {
  console.log(getCallerName());
}

class A {
  constructor() {
    console.log(getCallerName());
  }
  
  hello() {
    console.log(getCallerName());
  }
}

function main() {
  hello(); // Prints: main
  
  const a = new A(); // Prints: main
  a.hello(); // Prints: main
}

main();

I wanted to add my fiddle here for this:

http://jsfiddle.net/bladnman/EhUm3/

I tested this is chrome, safari and IE (10 and 8). Works fine. There is only 1 function that matters, so if you get scared by the big fiddle, read below.

Note: There is a fair amount of my own "boilerplate" in this fiddle. You can remove all of that and use split's if you like. It's just an ultra-safe" set of functions I've come to rely on.

There is also a "JSFiddle" template in there that I use for many fiddles to simply quick fiddling.

If you just want the function name and not the code, and want a browser-independent solution, use the following:

var callerFunction = arguments.callee.caller.toString().match(/function ([^\(]+)/)[1];

Note that the above will return an error if there is no caller function as there is no [1] element in the array. To work around, use the below:

var callerFunction = (arguments.callee.caller.toString().match(/function ([^\(]+)/) === null) ? 'Document Object Model': arguments.callee.caller.toString().match(/function ([^\(]+)/)[1], arguments.callee.toString().match(/function ([^\(]+)/)[1]);

Here, everything but the functionname is stripped from caller.toString(), with RegExp.

<!DOCTYPE html>
<meta charset="UTF-8">
<title>Show the callers name</title><!-- This validates as html5! -->
<script>
main();
function main() { Hello(); }
function Hello(){
  var name = Hello.caller.toString().replace(/\s\([^#]+$|^[^\s]+\s/g,'');
  name = name.replace(/\s/g,'');
  if ( typeof window[name] !== 'function' )
    alert ("sorry, the type of "+name+" is "+ typeof window[name]);
  else
    alert ("The name of the "+typeof window[name]+" that called is "+name);
}
</script>

Just want to let you know that on PhoneGap/Android the name doesnt seem to be working. But arguments.callee.caller.toString() will do the trick.

Note you can't use Function.caller in Node.js, use caller-id package instead. For example:

var callerId = require('caller-id');

function foo() {
    bar();
}
function bar() {
    var caller = callerId.getData();
    /*
    caller = {
        typeName: 'Object',
        functionName: 'foo',
        filePath: '/path/of/this/file.js',
        lineNumber: 5,
        topLevelFlag: true,
        nativeFlag: false,
        evalFlag: false
    }
    */
}

here is a function to get full stacktrace:

function stacktrace() {
var f = stacktrace;
var stack = 'Stack trace:';
while (f) {
  stack += '\n' + f.name;
  f = f.caller;
}
return stack;
}

Works great for me, and you can chose how much you want to go back in the functions:

function getCaller(functionBack= 0) {
    const back = functionBack * 2;
    const stack = new Error().stack.split('at ');
    const stackIndex = stack[3 + back].includes('C:') ? (3 + back) : (4 + back);
    const isAsync = stack[stackIndex].includes('async');
    let result;
    if (isAsync)
      result = stack[stackIndex].split(' ')[1].split(' ')[0];
    else
      result = stack[stackIndex].split(' ')[0];
    return result;
}

I could use these in 2021 and get the stack which starts from the caller function :

1. console.trace();
2. console.log((new Error).stack)

// do the same as #2 just with better view
3. console.log((new Error).stack.split("\n")) 

Try the following code:

function getStackTrace(){
  var f = arguments.callee;
  var ret = [];
  var item = {};
  var iter = 0;

  while ( f = f.caller ){
      // Initialize
    item = {
      name: f.name || null,
      args: [], // Empty array = no arguments passed
      callback: f
    };

      // Function arguments
    if ( f.arguments ){
      for ( iter = 0; iter<f.arguments.length; iter++ ){
        item.args[iter] = f.arguments[iter];
      }
    } else {
      item.args = null; // null = argument listing not supported
    }

    ret.push( item );
  }
  return ret;
}

Worked for me in Firefox-21 and Chromium-25.

With Strict Mode On/Off (JavaScript & TypeScript), if (!) the caller exist you can try this one

console.log(`caller:${(new Error()).stack?.split('\n')[2].trim().split(' ')[1]}`)

Another way around this problem is to simply pass the name of the calling function as a parameter.

For example:

function reformatString(string, callerName) {

    if (callerName === "uid") {
        string = string.toUpperCase();
    }

    return string;
}

Now, you could call the function like this:

function uid(){
    var myString = "apples";

    reformatString(myString, function.name);
}

My example uses a hard coded check of the function name, but you could easily use a switch statement or some other logic to do what you want there.

As far as I know, we have 2 way for this from given sources like this-

1. arguments.caller

   function whoCalled()
   {
       if (arguments.caller == null)
          console.log('I was called from the global scope.');
       else
          console.log(arguments.caller + ' called me!');
   }
   

2. Function.caller

   function myFunc()
   {
      if (myFunc.caller == null) {
         return 'The function was called from the top!';
      }
      else
      {
         return 'This function\'s caller was ' + myFunc.caller;
       }
   }
   

Think u have your answer :).

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