Why does .trim() work in Mozilla but throws an error in IE8?

Using .trim() in JavaScript: Challenges in IE

While the .trim() method is widely used in JavaScript to remove leading and trailing whitespace from strings, users may encounter issues when using it in Internet Explorer (IE) browsers. This common problem has prompted the following question:

Question:

When attempting to apply .trim() to a string in JavaScript under Mozilla, it operates successfully. However, utilizing the same code in IE8 results in an error. What is the explanation for this disparity, and are there any solutions to make .trim() compatible with IE?

Code Excerpt:

var ID = document.getElementByID('rep_id').value.trim();

Error Message:

Message: Object doesn't support this property or method
Line: 604
Char: 2
Code: 0
URI: http://test.localhost/test.js

Answer:

The reason for the error in IE is that the .trim() method is not a built-in function in IE versions prior to IE9. To resolve this issue and provide .trim() functionality in IE, you can implement the following code:

if(typeof String.prototype.trim !== 'function') {
  String.prototype.trim = function() {
    return this.replace(/^\s+|\s+$/g, ''); 
  }
}

This code extends the String prototype to include the .trim() method. It utilizes regular expressions to match and remove leading and trailing whitespace. By adding this code to your script, .trim() can be seamlessly used in IE as well.

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