47 lines
1.9 KiB
JavaScript
47 lines
1.9 KiB
JavaScript
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// 26.1.2 Reflect.construct(target, argumentsList [, newTarget])
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var $export = require('./_export')
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, create = require('./_object-create')
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, aFunction = require('./_a-function')
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, anObject = require('./_an-object')
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, isObject = require('./_is-object')
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, fails = require('./_fails')
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, bind = require('./_bind')
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, rConstruct = (require('./_global').Reflect || {}).construct;
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// MS Edge supports only 2 arguments and argumentsList argument is optional
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// FF Nightly sets third argument as `new.target`, but does not create `this` from it
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var NEW_TARGET_BUG = fails(function(){
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function F(){}
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return !(rConstruct(function(){}, [], F) instanceof F);
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});
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var ARGS_BUG = !fails(function(){
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rConstruct(function(){});
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});
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$export($export.S + $export.F * (NEW_TARGET_BUG || ARGS_BUG), 'Reflect', {
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construct: function construct(Target, args /*, newTarget*/){
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aFunction(Target);
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anObject(args);
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var newTarget = arguments.length < 3 ? Target : aFunction(arguments[2]);
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if(ARGS_BUG && !NEW_TARGET_BUG)return rConstruct(Target, args, newTarget);
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if(Target == newTarget){
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// w/o altered newTarget, optimization for 0-4 arguments
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switch(args.length){
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case 0: return new Target;
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case 1: return new Target(args[0]);
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case 2: return new Target(args[0], args[1]);
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case 3: return new Target(args[0], args[1], args[2]);
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case 4: return new Target(args[0], args[1], args[2], args[3]);
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}
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// w/o altered newTarget, lot of arguments case
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var $args = [null];
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$args.push.apply($args, args);
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return new (bind.apply(Target, $args));
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}
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// with altered newTarget, not support built-in constructors
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var proto = newTarget.prototype
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, instance = create(isObject(proto) ? proto : Object.prototype)
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, result = Function.apply.call(Target, instance, args);
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return isObject(result) ? result : instance;
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}
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});
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