47 lines
1.3 KiB
JavaScript
47 lines
1.3 KiB
JavaScript
'use strict';
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var $TypeError = require('es-errors/type');
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var callBound = require('call-bind/callBound');
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var $charAt = callBound('String.prototype.charAt');
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var $stringToString = callBound('String.prototype.toString');
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var CanonicalNumericIndexString = require('./CanonicalNumericIndexString');
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var IsInteger = require('./IsInteger');
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var IsPropertyKey = require('./IsPropertyKey');
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var Type = require('./Type');
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var isNegativeZero = require('is-negative-zero');
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// https://262.ecma-international.org/8.0/#sec-stringgetownproperty
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module.exports = function StringGetOwnProperty(S, P) {
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var str;
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if (Type(S) === 'Object') {
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try {
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str = $stringToString(S);
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} catch (e) { /**/ }
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}
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if (typeof str !== 'string') {
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throw new $TypeError('Assertion failed: `S` must be a boxed string object');
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}
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if (!IsPropertyKey(P)) {
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throw new $TypeError('Assertion failed: IsPropertyKey(P) is not true');
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}
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if (typeof P !== 'string') {
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return void undefined;
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}
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var index = CanonicalNumericIndexString(P);
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var len = str.length;
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if (typeof index === 'undefined' || !IsInteger(index) || isNegativeZero(index) || index < 0 || len <= index) {
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return void undefined;
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}
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var resultStr = $charAt(S, index);
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return {
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'[[Configurable]]': false,
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'[[Enumerable]]': true,
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'[[Value]]': resultStr,
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'[[Writable]]': false
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};
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};
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