With the recent talk of JavaScript 1.9 there’s been some confusion as to what exactly that version means – especially in relation to other browsers. Here’s a quick breakdown: IE 6-7 support JScript 5 (which is equivalent to ECMAScript 3, JavaScript 1.5) IE 8 supports JScript 6 (which is equivalent to ECMAScript 3, JavaScript 1.5 – more bug fixes over JScript 5) Firefox 1.0 supports JavaScript 1.5

