84 lines
2.3 KiB
JavaScript
84 lines
2.3 KiB
JavaScript
Array.prototype.map = function(callback, thisArg) {
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var T, A, k;
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if (this == null) {
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throw new TypeError(' this is null or not defined');
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}
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// 1. Let O be the result of calling ToObject passing the |this|
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// value as the argument.
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var O = Object(this);
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// 2. Let lenValue be the result of calling the Get internal
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// method of O with the argument "length".
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// 3. Let len be ToUint32(lenValue).
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var len = O.length >>> 0;
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// 4. If IsCallable(callback) is false, throw a TypeError exception.
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// See: http://es5.github.com/#x9.11
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if (typeof callback !== 'function') {
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throw new TypeError(callback + ' is not a function');
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}
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// 5. If thisArg was supplied, let T be thisArg; else let T be undefined.
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if (arguments.length > 1) {
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T = thisArg;
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}
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// 6. Let A be a new array created as if by the expression new Array(len)
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// where Array is the standard built-in constructor with that name and
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// len is the value of len.
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A = new Array(len);
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// 7. Let k be 0
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k = 0;
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// 8. Repeat, while k < len
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while (k < len) {
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var kValue, mappedValue;
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// a. Let Pk be ToString(k).
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// This is implicit for LHS operands of the in operator
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// b. Let kPresent be the result of calling the HasProperty internal
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// method of O with argument Pk.
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// This step can be combined with c
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// c. If kPresent is true, then
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if (k in O) {
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// i. Let kValue be the result of calling the Get internal
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// method of O with argument Pk.
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kValue = O[k];
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// ii. Let mappedValue be the result of calling the Call internal
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// method of callback with T as the this value and argument
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// list containing kValue, k, and O.
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mappedValue = callback.call(T, kValue, k, O);
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// iii. Call the DefineOwnProperty internal method of A with arguments
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// Pk, Property Descriptor
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// { Value: mappedValue,
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// Writable: true,
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// Enumerable: true,
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// Configurable: true },
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// and false.
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// In browsers that support Object.defineProperty, use the following:
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// Object.defineProperty(A, k, {
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// value: mappedValue,
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// writable: true,
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// enumerable: true,
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// configurable: true
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// });
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// For best browser support, use the following:
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A[k] = mappedValue;
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}
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// d. Increase k by 1.
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k++;
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}
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// 9. return A
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return A;
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}; |