How to get all over 1000 klines in javascript without using third party functions

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Although there are already several APIs that include this functionality, it does not hurt to know how to implement it so as not to depend on third-party functions, I share this code snippet that I wrote myself and that I hope will help you in your own applications, it still requires validation code. but it works in the cases that the data is passed correctly, I also wait for corrections of it from you to improve it little by little

const burl = 'https://api.binance.com';
const bwsurl = 'wss://stream.binance.com:9443/ws/';
const intervals = {
	'1m': {
		'ms': 1000 * 60,
		'intervalNum': 1,
		'intervalLetter': 'm'
	},
	'3m': {
		'ms': 1000 * 60 * 3,
		'intervalNum': 3,
		'intervalLetter': 'm'	
	},
	'5m': {
		'ms': 1000 * 60 * 5,
		'intervalNum': 5,
		'intervalLetter': 'm'
	},
	'15m': {
		'ms': 1000 * 60 * 15,
		'intervalNum': 15,
		'intervalLetter': 'm'
	},
	'30m': {
		'ms': 1000 * 60 * 30,
		'intervalNum': 30,
		'intervalLetter': 'm'
	},
	'1h': {
		'ms': 1000 * 60 * 60,
		'intervalNum': 1,
		'intervalLetter': 'h'
	},
	'2h': {
		'ms': 1000 * 60 * 60 * 2,
		'intervalNum': 2,
		'intervalLetter': 'h'
	},
	'4h': {
		'ms': 1000 * 60 * 60 * 4,
		'intervalNum': 4,
		'intervalLetter':	'h'
	},
	'6h': {
		'ms': 1000 * 60 * 60 * 6,
		'intervalNum': 6,
		'intervalLetter':	'h'
	},
	'8h': {
		'ms': 1000 * 60 * 60 * 8,
		'intervalNum': 8,
		'intervalLetter':	'h'
	},
	'12h': {
		'ms': 1000 * 60 * 60 * 12,
		'intervalNum': 12,
		'intervalLetter':	'h'
	},
	'1d': {
		'ms': 1000 * 60 * 60 * 24,
		'intervalNum': 1,
		'intervalLetter':	'd'
	},
	'3d': {
		'ms': 1000 * 60 * 60 * 24 * 3,
		'intervalNum': 3,
		'intervalLetter':	'd'
	},
	'1w': {
		'ms': 1000 * 60 * 60 * 24 * 7,
		'intervalNum': 1,
		'intervalLetter':	'w'
	},
	'1M': {
		'ms': 1000 * 60 * 60 * 24 * 30,
		'intervalNum': 1,
		'intervalLetter':	'M'
	}
};

function klines(symbol = ‘BTCUSDT’, interval = ‘1d’, limit = 1000, startTime = null, endTime = null, callback = () => {}) {
extKlines(klArray = , symbol, interval, limit, startTime, endTime, callback);
}

function extKlines(klArray, symbol, interval, limit, startTime, endTime, callback) {
var endpoint = ‘/api/v3/klines’,
url = burl + endpoint + ‘?symbol=’ + symbol + ‘&interval=’ + interval;

if(limit > 0) {
	
	var xhttp = new XMLHttpRequest();
	url += '&limit=' + (limit > 1000 ? 1000 : limit);
	url += '&startTime=' + (startTime ? startTime : Date.now() - (intervals[interval].ms * limit));
	url += endTime ? (limit > 1000 ?  '' : '&endTime=' + endTime) : '';
	
	xhttp.responseType = 'json';

	xhttp.onreadystatechange = function () {
		if (this.readyState == 4 && this.status == 200){
			klArray.length != 0 ? klArray = klArray.concat(this.response) : klArray = this.response;				
			limit -= 1000;
			startTime = this.response[this.response.length - 1][0] + intervals[interval].ms;
			
			setTimeout(extKlines(klArray, symbol, interval, limit, startTime, endTime, callback), 1000);
		}
	};

	xhttp.open('GET', url, true);
	xhttp.send();
}else{
	callback(klArray);
}

}