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32 lines
1.4 KiB
32 lines
1.4 KiB
'use strict'; |
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var $ = require('../internals/export'); |
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var getOwnPropertyDescriptor = require('../internals/object-get-own-property-descriptor').f; |
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var toLength = require('../internals/to-length'); |
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var notARegExp = require('../internals/not-a-regexp'); |
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var requireObjectCoercible = require('../internals/require-object-coercible'); |
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var correctIsRegExpLogic = require('../internals/correct-is-regexp-logic'); |
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var IS_PURE = require('../internals/is-pure'); |
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var nativeStartsWith = ''.startsWith; |
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var min = Math.min; |
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var CORRECT_IS_REGEXP_LOGIC = correctIsRegExpLogic('startsWith'); |
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// https://github.com/zloirock/core-js/pull/702 |
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var MDN_POLYFILL_BUG = !IS_PURE && !CORRECT_IS_REGEXP_LOGIC && !!function () { |
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var descriptor = getOwnPropertyDescriptor(String.prototype, 'startsWith'); |
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return descriptor && !descriptor.writable; |
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}(); |
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// `String.prototype.startsWith` method |
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// https://tc39.github.io/ecma262/#sec-string.prototype.startswith |
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$({ target: 'String', proto: true, forced: !MDN_POLYFILL_BUG && !CORRECT_IS_REGEXP_LOGIC }, { |
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startsWith: function startsWith(searchString /* , position = 0 */) { |
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var that = String(requireObjectCoercible(this)); |
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notARegExp(searchString); |
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var index = toLength(min(arguments.length > 1 ? arguments[1] : undefined, that.length)); |
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var search = String(searchString); |
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return nativeStartsWith |
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? nativeStartsWith.call(that, search, index) |
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: that.slice(index, index + search.length) === search; |
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} |
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});
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