com.google.javascript.jscomp.js.es6.string.startswith.js Maven / Gradle / Ivy
/*
* Copyright 2016 The Closure Compiler Authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
'require util/checkstringargs';
'require util/polyfill';
$jscomp.polyfill('String.prototype.startsWith', function(orig) {
if (orig) return orig;
/**
* Tests whether the string starts with a given substring.
*
* Polyfills the instance method String.prototype.startsWith().
*
* @this {string}
* @param {string} searchString
* @param {number=} opt_position
* @return {boolean}
*/
var polyfill = function(searchString, opt_position) {
'use strict';
var string = $jscomp.checkStringArgs(this, searchString, 'startsWith');
searchString = searchString + '';
var strLen = string.length;
var searchLen = searchString.length;
var i = Math.max(
0,
Math.min(/** @type {number} */ (opt_position) | 0, string.length));
var j = 0;
while (j < searchLen && i < strLen) {
if (string[i++] != searchString[j++]) return false;
}
return j >= searchLen;
};
return polyfill;
}, 'es6', 'es3');