Add unicode_length to count the correct number of characters in the string and fix incorrect index problem of codePointAt api

unicode.fix.js

/**
	ISC License

	Copyright (c) 2018, JCloudYu

	Permission to use, copy, modify, and/or distribute this software for any
	purpose with or without fee is hereby granted, provided that the above
	copyright notice and this permission notice appear in all copies.

	THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
	WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
	MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
	ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
	WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
	ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
	OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
**/

Object.defineProperty(String.prototype, '_codePointAt', {value:String.prototype.codePointAt, enumerable:false});
String.prototype.codePointAt = function(index){
	let _cur_index = 0, _code_point = undefined;
	for( let i=0; i<this.length; i++ ) {
		let codePoint = this._codePointAt(i);
		if ( _cur_index === index ) {
			_code_point = codePoint;
			break;
		}
		
		_cur_index++;
		
		// If the code point requires surrogate pairs, then skip the up coming byte
		if ( codePoint > 0xFFFF ) { i++; }
	}
	
	return _code_point;
};
Object.defineProperty(String.prototype, 'unicode_length', { get:function(){
	let _char_length = 0;
	for( let i=0; i<this.length; i++ ) {
		_char_length++;
		let codePoint = this._codePointAt(i);
		// If the code point requires surrogate pairs, then skip the up coming byte
		if ( codePoint > 0xFFFF ) { i++; }
	}
	return _char_length;
}, enumerable:true, configurable:true });


/*
	//Testing code
	let char = '012𠮷45我6789ABCDE𠁎';
	for( let i=0; i<char.unicode_length; i++ ) {
		console.log(`${i}: ${char.codePointAt(i)}`);
	}
*/