Constnium/node_modules/es-abstract/2015/StringGetIndexProperty.js
2022-06-23 02:27:43 +02:00

52 lines
1.3 KiB
JavaScript

'use strict';
var GetIntrinsic = require('get-intrinsic');
var callBound = require('call-bind/callBound');
var $TypeError = GetIntrinsic('%TypeError%');
var $charAt = callBound('String.prototype.charAt');
var isString = require('is-string');
var isNegativeZero = require('is-negative-zero');
var unbox = require('unbox-primitive');
var CanonicalNumericIndexString = require('./CanonicalNumericIndexString');
var IsInteger = require('./IsInteger');
var IsPropertyKey = require('./IsPropertyKey');
var Type = require('./Type');
// https://262.ecma-international.org/6.0/#sec-stringgetindexproperty
module.exports = function StringGetIndexProperty(S, P) {
if (typeof S === 'string' || !isString(S)) {
throw new $TypeError('Assertion failed: `S` must be a boxed String Object');
}
if (!IsPropertyKey(P)) {
throw new $TypeError('Assertion failed: `P` must be a Property Key');
}
if (Type(P) !== 'String') {
return void undefined;
}
var index = CanonicalNumericIndexString(P);
if (typeof index === 'undefined' || !IsInteger(index) || isNegativeZero(index)) {
return void undefined;
}
var str = unbox(S);
var len = str.length;
if (index < 0 || len <= index) {
return void undefined;
}
var resultStr = $charAt(str, index);
return {
'[[Configurable]]': false,
'[[Enumerable]]': true,
'[[Value]]': resultStr,
'[[Writable]]': false
};
};