37 lines
1.1 KiB
Plaintext
37 lines
1.1 KiB
Plaintext
'use strict';
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var callBound = require('call-bound');
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var $TypeError = require('es-errors/type');
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var isInteger = require('math-intrinsics/isInteger');
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var $slice = callBound('String.prototype.slice');
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// https://262.ecma-international.org/16.0/#sec-stringindexof
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module.exports = function StringIndexOf(string, searchValue, fromIndex) {
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if (typeof string !== 'string') {
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throw new $TypeError('Assertion failed: `string` must be a String');
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}
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if (typeof searchValue !== 'string') {
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throw new $TypeError('Assertion failed: `searchValue` must be a String');
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}
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if (!isInteger(fromIndex) || fromIndex < 0) {
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throw new $TypeError('Assertion failed: `fromIndex` must be a non-negative integer');
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}
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var len = string.length; // step 1
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if (searchValue === '' && fromIndex <= len) {
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return fromIndex; // step 2
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}
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var searchLen = searchValue.length; // step 3
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for (var i = fromIndex; i <= (len - searchLen); i += 1) { // step 4
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var candidate = $slice(string, i, i + searchLen); // step 4.a
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if (candidate === searchValue) {
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return i; // step 4.b
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}
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}
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return 'NOT-FOUND'; // step 5
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};
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