How to get function parameter names values dynamically

Question

Is there a way to get the function parameter names of a function dynamically?

Let’s say my function looks like this:

function doSomething(param1, param2, .... paramN){
   // fill an array with the parameter name and value
   // some other code 
}

Now, how would I get a list of the parameter names and their values into an array from inside the function?

Answer 1

Hello @kartik,

The following function will return an array of the parameter names of any function passed in.

var STRIP_COMMENTS = /((\/\/.*$)|(\/\*[\s\S]*?\*\/))/mg;
var ARGUMENT_NAMES = /([^\s,]+)/g;
function getParamNames(func) {
  var fnStr = func.toString().replace(STRIP_COMMENTS, '');
  var result = fnStr.slice(fnStr.indexOf('(')+1, fnStr.indexOf(')')).match(ARGUMENT_NAMES);
  if(result === null)
     result = [];
  return result;
}

Example usage:

getParamNames(getParamNames) // returns ['func']
getParamNames(function (a,b,c,d){}) // returns ['a','b','c','d']
getParamNames(function (a,/*b,c,*/d){}) // returns ['a','d']
getParamNames(function (){}) // returns []

Hope it helps!!
Thank You!!