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'use strict'; |
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var ERROR_MESSAGE = 'Function.prototype.bind called on incompatible '; |
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var slice = Array.prototype.slice; |
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var toStr = Object.prototype.toString; |
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var funcType = '[object Function]'; |
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module.exports = function bind(that) { |
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var target = this; |
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if (typeof target !== 'function' || toStr.call(target) !== funcType) { |
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throw new TypeError(ERROR_MESSAGE + target); |
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} |
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var args = slice.call(arguments, 1); |
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var bound; |
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var binder = function () { |
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if (this instanceof bound) { |
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var result = target.apply( |
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this, |
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args.concat(slice.call(arguments)) |
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); |
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if (Object(result) === result) { |
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return result; |
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} |
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return this; |
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} else { |
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return target.apply( |
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that, |
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args.concat(slice.call(arguments)) |
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); |
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} |
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}; |
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var boundLength = Math.max(0, target.length - args.length); |
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var boundArgs = []; |
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for (var i = 0; i < boundLength; i++) { |
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boundArgs.push('$' + i); |
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} |
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bound = Function('binder', 'return function (' + boundArgs.join(',') + '){ return binder.apply(this,arguments); }')(binder); |
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if (target.prototype) { |
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var Empty = function Empty() {}; |
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Empty.prototype = target.prototype; |
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bound.prototype = new Empty(); |
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Empty.prototype = null; |
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} |
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return bound; |
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}; |
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