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- '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/16.0/#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; // step 1
- if (searchValue === '' && fromIndex <= len) {
- return fromIndex; // step 2
- }
- var searchLen = searchValue.length; // step 3
- for (var i = fromIndex; i <= (len - searchLen); i += 1) { // step 4
- var candidate = $slice(string, i, i + searchLen); // step 4.a
- if (candidate === searchValue) {
- return i; // step 4.b
- }
- }
- return 'NOT-FOUND'; // step 5
- };
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