| 'use strict'; |
| |
| var callBound = require('call-bound'); |
| |
| var $TypeError = require('es-errors/type'); |
| var isInteger = require('math-intrinsics/isInteger'); |
| |
| var $slice = callBound('String.prototype.slice'); |
| |
| // https://262.ecma-international.org/12.0/#sec-stringindexof |
| |
| module.exports = function StringIndexOf(string, searchValue, fromIndex) { |
| if (typeof string !== 'string') { |
| throw new $TypeError('Assertion failed: `string` must be a String'); |
| } |
| if (typeof searchValue !== 'string') { |
| throw new $TypeError('Assertion failed: `searchValue` must be a String'); |
| } |
| if (!isInteger(fromIndex) || fromIndex < 0) { |
| throw new $TypeError('Assertion failed: `fromIndex` must be a non-negative integer'); |
| } |
| |
| var len = string.length; |
| if (searchValue === '' && fromIndex <= len) { |
| return fromIndex; |
| } |
| |
| var searchLen = searchValue.length; |
| for (var i = fromIndex; i <= (len - searchLen); i += 1) { |
| var candidate = $slice(string, i, i + searchLen); |
| if (candidate === searchValue) { |
| return i; |
| } |
| } |
| return -1; |
| }; |