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if (!Array.prototype.indexOf) {
Array.prototype.indexOf = function (searchElement, fromIndex) {
if ( this === undefined || this === null ) {
throw new TypeError( '"this" is null or not defined' );
}
var length = this.length >>> 0; // Hack to convert object.length to a UInt32
fromIndex = +fromIndex || 0;
if (Math.abs(fromIndex) === Infinity) {
fromIndex = 0;
}
if (fromIndex < 0) {
fromIndex += length;
if (fromIndex < 0) {
fromIndex = 0;
}
}
for (;fromIndex < length; fromIndex++) {
if (this[fromIndex] === searchElement) {
return fromIndex;
}
}
return -1;
};
}
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@jdalton jdalton commented Feb 21, 2014

The in check would be:

if (fromIndex in this && this[fromIndex] === searchElement) {
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@jdalton jdalton commented Feb 21, 2014

This polyfill is missing other steps, like converting this to an object, that es5-shim covers.

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