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Array index handling

Starting with Windows Internet Explorer 9, array elements with large indices are handled differently than in earlier versions.

Windows Internet Explorer 8 does not conform to the ECMAScript (3rd edition) specification in situations where the initial value of the array's length property is greater than 2E+31-1 (that is, 2147483647). When an Array element is created with an index greater than 2147483647, the index of new element created will be a negative integer.

Internet Explorer 9 correctly handles Array elements that use indices between 2E+31-1 and 2E+32-2. The Internet Explorer 8 behavior is not replicated in any of the Internet Explorer 9 document modes.

This can be observed when an element is pushed to an array of length 2E+31-1.

If your webpage uses large arrays, test your code between Internet Explorer 8 and Internet Explorer 9.

The following example prints "true" in Internet Explorer 8, but prints "false" in Internet Explorer 9.


function test() {
    var arr = new Array();		
    arr[2147483650] = 10000;
    arr.push(10);	
    document.write(arr["-2147483645"] == 10);
}
test();

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