52 lines
2.1 KiB
JavaScript
52 lines
2.1 KiB
JavaScript
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var $ = require('../internals/export');
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var getBuiltIn = require('../internals/get-built-in');
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var aFunction = require('../internals/a-function');
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var anObject = require('../internals/an-object');
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var isObject = require('../internals/is-object');
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var create = require('../internals/object-create');
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var bind = require('../internals/function-bind');
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var fails = require('../internals/fails');
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var nativeConstruct = getBuiltIn('Reflect', 'construct');
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// `Reflect.construct` method
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// https://tc39.github.io/ecma262/#sec-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 !(nativeConstruct(function () { /* empty */ }, [], F) instanceof F);
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});
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var ARGS_BUG = !fails(function () {
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nativeConstruct(function () { /* empty */ });
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});
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var FORCED = NEW_TARGET_BUG || ARGS_BUG;
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$({ target: 'Reflect', stat: true, forced: FORCED, sham: FORCED }, {
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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 nativeConstruct(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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