38 lines
1.0 KiB
JavaScript
38 lines
1.0 KiB
JavaScript
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'use strict';
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var callBound = require('call-bind/callBound');
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var $TypeError = require('es-errors/type');
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var isInteger = require('../helpers/isInteger');
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var $slice = callBound('String.prototype.slice');
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// https://262.ecma-international.org/12.0/#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;
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if (searchValue === '' && fromIndex <= len) {
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return fromIndex;
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}
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var searchLen = searchValue.length;
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for (var i = fromIndex; i <= (len - searchLen); i += 1) {
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var candidate = $slice(string, i, i + searchLen);
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if (candidate === searchValue) {
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return i;
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}
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}
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return -1;
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};
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