core-js/modules/es.string.starts-with.js

'use strict';
var $ = require('../internals/export');
var uncurryThis = require('../internals/function-uncurry-this-clause');
var getOwnPropertyDescriptor = require('../internals/object-get-own-property-descriptor').f;
var toLength = require('../internals/to-length');
var toString = require('../internals/to-string');
var notARegExp = require('../internals/not-a-regexp');
var requireObjectCoercible = require('../internals/require-object-coercible');
var correctIsRegExpLogic = require('../internals/correct-is-regexp-logic');
var IS_PURE = require('../internals/is-pure');

var stringSlice = uncurryThis(''.slice);
var min = Math.min;

var CORRECT_IS_REGEXP_LOGIC = correctIsRegExpLogic('startsWith');
// https://github.com/zloirock/core-js/pull/702
var MDN_POLYFILL_BUG = !IS_PURE && !CORRECT_IS_REGEXP_LOGIC && !!function () {
  var descriptor = getOwnPropertyDescriptor(String.prototype, 'startsWith');
  return descriptor && !descriptor.writable;
}();

// `String.prototype.startsWith` method
// https://tc39.es/ecma262/#sec-string.prototype.startswith
$({ target: 'String', proto: true, forced: !MDN_POLYFILL_BUG && !CORRECT_IS_REGEXP_LOGIC }, {
  startsWith: function startsWith(searchString /* , position = 0 */) {
    var that = toString(requireObjectCoercible(this));
    notARegExp(searchString);
    var index = toLength(min(arguments.length > 1 ? arguments[1] : undefined, that.length));
    var search = toString(searchString);
    return stringSlice(that, index, index + search.length) === search;
  }
});