How Can You Retrieve a Function\'s Name in JavaScript?

Accessing Function Names Within Their Scope

The ability to retrieve a function's name from within the function itself is a useful technique in JavaScript. However, this can be challenging since function names are not readily available when accessing them from inside.

ES6 Solution:

In ES6, accessing a function's name is straightforward:

<code class="javascript">const getFunctionName = () => myFunction.name;</code>

ES5 Solution:

For ES5, the following approach is recommended:

<code class="javascript">function getFunctionName(func) {
  const funcStr = func.toString();
  const name = funcStr.substring('function '.length, funcStr.indexOf('('));
  return name;
}</code>

Using Function.caller (Not Recommended):

Function.caller provides a non-standard solution for accessing the caller's name. However, it should be avoided due to potential compatibility issues and its deprecation in strict mode.

Regex-Based Solution:

Another efficient ES5 approach involves using a regular expression:

<code class="javascript">const getFunctionName = (func) => /function\s+([a-zA-Z$][a-zA-Z$0-9]+)/.exec(func.toString())[1];</code>

Example:

Let's use the provided code snippet as an example:

<code class="javascript">var ns.parent = function() {
  // at this point, i want to know who the child is that called the parent
  // ie
  console.log(getFunctionName(this));
}

var obj = new ns.parent.child();</code>

This will output: "newFunc" because newFunc is the function that called the parent function.

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