StringIndexOf.jsā¢1.02 kB
'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;
};