51 lines
1.3 KiB
JavaScript
51 lines
1.3 KiB
JavaScript
'use strict';
|
|
|
|
var callBound = require('call-bind/callBound');
|
|
|
|
var $TypeError = require('es-errors/type');
|
|
|
|
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');
|
|
|
|
// 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 (typeof 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
|
|
};
|
|
};
|