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rwaldron/index.js

Created July 27, 2012 07:01
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Revisions

  1. rwaldron created this gist Jul 27, 2012.
    153 changes: 153 additions & 0 deletions index.js
    View file
    Original file line number Diff line number Diff line change
    @@ -0,0 +1,153 @@
    (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) );
    }