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- 'use strict';
- var GetIntrinsic = require('get-intrinsic');
- var callBound = require('call-bind/callBound');
- var $TypeError = GetIntrinsic('%TypeError%');
- var IsIntegralNumber = require('./IsIntegralNumber');
- var StringToCodePoints = require('./StringToCodePoints');
- var Type = require('./Type');
- var $indexOf = callBound('String.prototype.indexOf');
- // https://ecma-international.org/ecma-262/13.0/#sec-getstringindex
- module.exports = function GetStringIndex(S, e) {
- if (Type(S) !== 'String') {
- throw new $TypeError('Assertion failed: `S` must be a String');
- }
- if (!IsIntegralNumber(e) || e < 0) {
- throw new $TypeError('Assertion failed: `e` must be a non-negative integer');
- }
- if (S === '') {
- return 0;
- }
- var codepoints = StringToCodePoints(S);
- var eUTF = e >= codepoints.length ? S.length : $indexOf(S, codepoints[e]);
- return eUTF;
- };
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