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48 lines
1.9 KiB
JavaScript
48 lines
1.9 KiB
JavaScript
5 years ago
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// 26.1.2 Reflect.construct(target, argumentsList [, newTarget])
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var $export = require('./_export');
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var create = require('./_object-create');
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var aFunction = require('./_a-function');
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var anObject = require('./_an-object');
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var isObject = require('./_is-object');
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var fails = require('./_fails');
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var bind = require('./_bind');
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var rConstruct = (require('./_global').Reflect || {}).construct;
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// MS Edge supports only 2 arguments and argumentsList argument is optional
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// FF Nightly sets third argument as `new.target`, but does not create `this` from it
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var NEW_TARGET_BUG = fails(function () {
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function F() { /* empty */ }
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return !(rConstruct(function () { /* empty */ }, [], F) instanceof F);
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});
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var ARGS_BUG = !fails(function () {
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rConstruct(function () { /* empty */ });
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});
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$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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var instance = create(isObject(proto) ? proto : Object.prototype);
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var 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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