Does JScript support string trim method?

Question

Whilst developing a Windows procedure using JScript, it seems that some string methods fail to work. In this example using trim, line 3 generates the runtime error:

"Object doesn't support this property or method".

My code:

strParent = "  a  ";
strParent = strParent.trim();
WScript.Echo ("Value: " + strParent);

Am I being stupid? Any ideas what the problem is?

Marker

Answer 1

JScript running under the Windows Scripting Host uses an old version of JScript based off of ECMAScript 3.0. The trim function was introduced in ECMAScript 5.0.

Swank

Thanks v. much Cheran. Back to the drawing board then! – Marker

Answer 2

You can add trim to the String class:

trim-test.js

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

strParent = "  a  ";
strParent = strParent.trim();
WScript.Echo ("Value: " + strParent);

Output from cmd.exe

C:\>cscript //nologo trim-test.js
Value: a

Drub

Answer 3

Use a polyfill, for example this one: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/Trim#Polyfill

This snippet:

if (!String.prototype.trim) {
  String.prototype.trim = function () {
    return this.replace(/^[\s\uFEFF\xA0]+|[\s\uFEFF\xA0]+$/g, '');
  };
}
strParent = "  a  ";
strParent = strParent.trim();
WScript.Echo ("Value: '" + strParent + "'");

will output

Value: 'a'

Degenerate