59 lines
1.7 KiB
JavaScript
59 lines
1.7 KiB
JavaScript
'use strict';
|
|
|
|
var GetIntrinsic = require('get-intrinsic');
|
|
|
|
var $TypeError = GetIntrinsic('%TypeError%');
|
|
var callBound = require('call-bind/callBound');
|
|
var isLeadingSurrogate = require('../helpers/isLeadingSurrogate');
|
|
var isTrailingSurrogate = require('../helpers/isTrailingSurrogate');
|
|
|
|
var Type = require('./Type');
|
|
var UTF16SurrogatePairToCodePoint = require('./UTF16SurrogatePairToCodePoint');
|
|
|
|
var $charAt = callBound('String.prototype.charAt');
|
|
var $charCodeAt = callBound('String.prototype.charCodeAt');
|
|
|
|
// https://262.ecma-international.org/12.0/#sec-codepointat
|
|
|
|
module.exports = function CodePointAt(string, position) {
|
|
if (Type(string) !== 'String') {
|
|
throw new $TypeError('Assertion failed: `string` must be a String');
|
|
}
|
|
var size = string.length;
|
|
if (position < 0 || position >= size) {
|
|
throw new $TypeError('Assertion failed: `position` must be >= 0, and < the length of `string`');
|
|
}
|
|
var first = $charCodeAt(string, position);
|
|
var cp = $charAt(string, position);
|
|
var firstIsLeading = isLeadingSurrogate(first);
|
|
var firstIsTrailing = isTrailingSurrogate(first);
|
|
if (!firstIsLeading && !firstIsTrailing) {
|
|
return {
|
|
'[[CodePoint]]': cp,
|
|
'[[CodeUnitCount]]': 1,
|
|
'[[IsUnpairedSurrogate]]': false
|
|
};
|
|
}
|
|
if (firstIsTrailing || (position + 1 === size)) {
|
|
return {
|
|
'[[CodePoint]]': cp,
|
|
'[[CodeUnitCount]]': 1,
|
|
'[[IsUnpairedSurrogate]]': true
|
|
};
|
|
}
|
|
var second = $charCodeAt(string, position + 1);
|
|
if (!isTrailingSurrogate(second)) {
|
|
return {
|
|
'[[CodePoint]]': cp,
|
|
'[[CodeUnitCount]]': 1,
|
|
'[[IsUnpairedSurrogate]]': true
|
|
};
|
|
}
|
|
|
|
return {
|
|
'[[CodePoint]]': UTF16SurrogatePairToCodePoint(first, second),
|
|
'[[CodeUnitCount]]': 2,
|
|
'[[IsUnpairedSurrogate]]': false
|
|
};
|
|
};
|