How Can I Dynamically Access Function Parameter Names and Values in JavaScript?

Intro to Function Parameter Access

Dynamically retrieving function parameter names and values can be a valuable technique for optimizing code. This article explores a comprehensive method to accomplish this task in various JavaScript environments.

Getting Function Parameter Names

The getParamNames function returns an array of parameter names for a given function. It employs a regular expression to extract parameter names from the function's source code. Here's the code:

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;
}

Getting Function Parameter Values

In addition to parameter names, you can also access parameter values using the arguments object within the function. This object contains a list of all parameters passed to the function.

Usage Example

To retrieve both parameter names and values:

function doSomething(param1, param2, .... paramN){
   // Convert arguments object to an array
   let argsArray = Array.from(arguments);

   // Create an array to store parameter data
   let paramData = [];

   // Loop through parameters
   for (let i = 0; i < argsArray.length; i++) {
     paramData.push({ name: getParamNames(doSomething)[i], value: argsArray[i] });
   }

   // Use the paramData array as needed
}

This example dynamically retrieves both parameter names and values, allowing you to access this information within the function.

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