Javascript IN operator compatibility

Question

Hi Folks,

Can someone tell me since which ECMA version the IN operator is available and which browsers (versions) support it ?

Explanation:

The IN-operator can be used like the following:

var myObject = {
    Firstname: 'Foo',
    Lastname: 'Bar'
};

if('Lastname' in myObject){
    // Lastname is an attribute of myObject
}

Answer 1

According to MDC, it's implemented in JavaScript 1.4.

According to Wikipedia:

• Netscape Navigator 6.0
• Firefox 1.0+
• IE 5.5+
• Opera 6.0+
• Safari 3.0+
• Chrome 1.0+

So I think you're probably OK :)

Answer 2

It is defined in ECMAScript 3rd edition. It is available in IE5.5-IE8 (JScript version 1), Firefox 1+, Chrome (all versions), Opera, Safari and probably most other javascript supporting browsers.

You can use it safe in the knowledge that it will work.

You should err on the side of caution when using it to check event support. All implementations except Mozilla support "eventname" in element as a test for DOM events, Firefox will result in false here unless a handler is defined.

"onclick" in document.body; // -> false in Fx, true in others
document.body.setAttribute("onclick", "");
typeof(document.body.onclick == "function") // -> true in Fx