Decimal Truncation in JavaScript

Newer browsers provide a new toFixed() function that does the trick:

var myVar = new Number(4.12345678);
var x = myVar.toFixed(3); // x = 4.123

For older browsers, a slightly more cumbersome method in needed:

var myVar = 4.12345678;
var x = parseInt(myVar * 1000) / 1000; // x = 4.123