Javascript IN operator compatibility

javascript ecma262
jAndy picture jAndy · May 27, 2010 · Viewed 11.1k times · Source

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

Andy E picture Andy E · May 27, 2010

It is defined in ECMAScript 3rd edition. It is available in IE 5.5+ and all in-use versions of Firefox, Chrome, Opera and Safari.

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 older Firefox versions support "eventname" in element as a test for DOM events.

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

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