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106 lines
4.4 KiB
JavaScript
106 lines
4.4 KiB
JavaScript
// Copyright 2015 Microsoft Corporation. All rights reserved.
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// This code is governed by the license found in the LICENSE file.
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/*---
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esid: sec-object.assign
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description: >
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Object.assign with an Array Exotic Object target employs the corresponding
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internal methods.
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info: |
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Object.assign ( _target_, ..._sources_ )
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3.a.iii.2.b. Perform ? Set(_to_, _nextKey_, _propValue_, *true*).
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Set ( _O_, _P_, _V_, _Throw_ )
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1. Let _success_ be ? _O_.[[Set]](_P_, _V_, _O_).
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OrdinarySet ( _O_, _P_, _V_, _Receiver_ )
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1. Let _ownDesc_ be ? _O_.[[GetOwnProperty]](_P_).
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2. Return ? OrdinarySetWithOwnDescriptor(_O_, _P_, _V_, _Receiver_, _ownDesc_).
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OrdinarySetWithOwnDescriptor ( _O_, _P_, _V_, _Receiver_, _ownDesc_ )
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1. If _ownDesc_ is *undefined*, then
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a. Let _parent_ be ? O.[[GetPrototypeOf]]().
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b. If _parent_ is not *null*, then
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i. Return ? _parent_.[[Set]](_P_, _V_, _Receiver_).
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c. Else,
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i. Set _ownDesc_ to the PropertyDescriptor { [[Value]]: *undefined*, [[Writable]]: *true*, [[Enumerable]]: *true*, [[Configurable]]: *true* }.
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2. If IsDataDescriptor(_ownDesc_) is *true*, then
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...
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c. Let _existingDescriptor_ be ? _Receiver_.[[GetOwnProperty]](_P_).
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d. If _existingDescriptor_ is not *undefined*, then
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...
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iii. Let _valueDesc_ be the PropertyDescriptor { [[Value]]: _V_ }.
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iv. Return ? _Receiver_.[[DefineOwnProperty]](_P_, _valueDesc_).
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e. Else,
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i. Assert: _Receiver_ does not currently have a property _P_.
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ii. Return ? CreateDataProperty(_Receiver_, _P_, _V_).
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CreateDataProperty ( _O_, _P_, _V_ )
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1. Let _newDesc_ be the PropertyDescriptor { [[Value]]: _V_, [[Writable]]: *true*, [[Enumerable]]: *true*, [[Configurable]]: *true* }.
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2. Return ? _O_.[[DefineOwnProperty]](_P_, _newDesc_).
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Array exotic object [[DefineOwnProperty]] ( _P_, _Desc_ )
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1. If _P_ is *"length"*, then
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a. Return ? ArraySetLength(_A_, _Desc_).
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2. Else if _P_ is an array index, then
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...
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k. If _index_ ≥ _length_, then
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i. Set _lengthDesc_.[[Value]] to _index_ + *1*𝔽.
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ii. Set _succeeded_ to ! OrdinaryDefineOwnProperty(_A_, *"length"*, _lengthDesc_).
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3. Return ? OrdinaryDefineOwnProperty(_A_, _P_, _Desc_).
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The Object Type
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An **integer index** is a property name _n_ such that CanonicalNumericIndexString(_n_) returns an
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integral Number in the inclusive interval from *+0*𝔽 to 𝔽(2**53 - 1). An **array index** is an
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integer index _n_ such that CanonicalNumericIndexString(_n_) returns an integral Number in the
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inclusive interval from *+0*𝔽 to 𝔽(2**32 - 2).
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---*/
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var target = [7, 8, 9];
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var result = Object.assign(target, [1]);
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assert.sameValue(result, target);
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assert.compareArray(result, [1, 8, 9],
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"elements must be assigned from an array source onto an array target");
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var sparseArraySource = [];
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sparseArraySource[2] = 3;
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result = Object.assign(target, sparseArraySource);
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assert.sameValue(result, target);
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assert.compareArray(result, [1, 8, 3], "holes in a sparse array source must not be copied");
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var shortObjectSource = { 1: 2, length: 2 };
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shortObjectSource["-0"] = -1;
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shortObjectSource["1.5"] = -2;
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shortObjectSource["4294967295"] = -3; // 2**32 - 1
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result = Object.assign(target, shortObjectSource);
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assert.sameValue(result, target);
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assert.compareArray(result, [1, 2],
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"array index properties must be copied from a non-array source");
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assert.sameValue(result["-0"], -1,
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"a property with name -0 must be assigned onto an array target");
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assert.sameValue(result["1.5"], -2,
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"a property with name 1.5 must be assigned onto an array target");
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assert.sameValue(result["4294967295"], -3,
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"a property with name 4294967295 (2**32 - 1) must be assigned onto an array target");
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result = Object.assign(target, { length: 1 });
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assert.sameValue(result, target);
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assert.compareArray(result, [1], "assigning a short length must shrink an array target");
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result = Object.assign(target, { 2: 0 });
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assert.sameValue(result, target);
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assert.compareArray(result, [1, undefined, 0],
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"assigning a high array index must grow an array target");
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if (typeof Proxy !== 'undefined') {
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var accordionSource = new Proxy({ length: 0, 1: 9 }, {
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ownKeys: function() {
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return ["length", "1"];
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}
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});
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result = Object.assign(target, accordionSource);
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assert.sameValue(result, target);
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assert.compareArray(result, [undefined, 9],
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"assigning a short length before a high array index must shrink and then grow an array target");
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}
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