Created
July 27, 2012 07:01
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Correct implementation of Array.from and Array.of as they are currently spec'ed. Includes "isConstructor"
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| (function( global ) { | |
| "use strict"; | |
| function isConstructor( C ) { | |
| try { | |
| new C(); | |
| return true; | |
| } catch ( e ) { | |
| return false; | |
| } | |
| } | |
| Array.from = function( arrayLike ) { | |
| var items, len, C, A, k, Pk, kPresent, kValue; | |
| // 1. Let items be ToObject(arrayLike). | |
| items = Object(arrayLike); | |
| // 3. Let lenValue be the result of calling the [[Get]] | |
| // internal method of items with the argument "length". | |
| // 4. Let len be ToInteger(lenValue). | |
| len = +items.length; | |
| // 6. Let C be the |this| value. | |
| C = this; | |
| // 7. If isConstructor(C) is true, then | |
| if ( isConstructor(C) ) { | |
| // a. Let newObj be the result of calling the | |
| // [[Construct]] internal method of C with an argument | |
| // list containing the single item len. | |
| // b. Let A be ToObject(newObj). | |
| A = Object(new C(len)); | |
| } else { | |
| A = new Array(len); | |
| } | |
| // 10. Let k be 0. | |
| k = 0; | |
| // 11. Repeat, while k < len | |
| while ( k < len ) { | |
| // a. Let Pk be ToString(k). | |
| Pk = String(k); | |
| // b. Let kPresent be the result of calling the [[HasProperty]] | |
| // internal method of items with argument Pk. | |
| kPresent = items.hasOwnProperty(Pk); | |
| // c. If kPresent is true, then... | |
| if ( kPresent ) { | |
| // i. Let kValue be the result of calling the [[Get]] | |
| // internal method of items with argument Pk. | |
| kValue = items[ Pk ]; | |
| // ii. ReturnIfAbrupt(kValue). | |
| // iii. Let defineStatus be the result of calling the | |
| // [[DefineOwnProperty]] internal method of A with | |
| // arguments Pk, Property Descriptor | |
| // {[[Value]]: kValue.[[value]], | |
| // [[Writable]]: true, | |
| // [[Enumerable]]: true, | |
| // [[Configurable]]: true}, and true. | |
| A[ k ] = kValue; | |
| } | |
| // d. Increase k by 1. | |
| k++; | |
| } | |
| // 14. Return A. | |
| return A; | |
| }; | |
| Array.of = function() { | |
| var items, len, C, A, k, Pk, kPresent, kValue; | |
| // X. Let items be ToObject(arrayLike). | |
| items = Object(arguments); | |
| // 1. Let lenValue be the result of calling the [[Get]] | |
| // internal method of items with the argument "length". | |
| // 2. Let len be ToInteger(lenValue). | |
| len = +items.length; | |
| // 3. Let C be the |this| value. | |
| C = this; | |
| // 4. If isConstructor(C) is true, then | |
| if ( isConstructor(C) ) { | |
| // a, b. | |
| A = Object(new C(len)); | |
| } else { | |
| // 5. Else, a. | |
| A = new Array(len); | |
| } | |
| // 6. omitted | |
| // 7. Let k be 0. | |
| k = 0; | |
| // 8. Repeat, while k < len | |
| while ( k < len ) { | |
| // a. Let Pk be ToString(k). | |
| Pk = String(k); | |
| // b. Let kValue be the result of calling the [[Get]] | |
| // internal method of items with argument Pk. | |
| kValue = items[ Pk ]; | |
| // c. Let defineStatus be the result of calling the | |
| // [[DefineOwnProperty]] internal method of A with | |
| // arguments Pk, Property Descriptor | |
| // {[[Value]]: kValue.[[value]], | |
| // [[Writable]]: true, | |
| // [[Enumerable]]: true, | |
| // [[Configurable]]: true}, and true. | |
| A[ k ] = kValue; | |
| // d. omitted | |
| // e. Increase k by 1. | |
| k++; | |
| } | |
| // 9, 10. omitted | |
| // 11. Return A. | |
| return A; | |
| }; | |
| global.Array.from = Array.from; | |
| global.Array.of = Array.of; | |
| })( global ); | |
| { | |
| // tests | |
| var arrayLike = { 0: "a", 1: "b", 2: "c", length: 3 }; | |
| console.log( Array.from(arrayLike) ); | |
| console.log( Array.of(0) ); | |
| console.log( Array.of(1, null, undefined, false, 2) ); | |
| console.log( Array.of() ); | |
| var other = { | |
| from: Array.from, | |
| of: Array.of | |
| }; | |
| console.log( other.from(arrayLike) ); | |
| console.log( other.of(1, null, undefined, false, 2) ); | |
| } |
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