33 lines
1.4 KiB
JavaScript
33 lines
1.4 KiB
JavaScript
'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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