JavaScript Realtime Ticking Stock Charts

1/**
2 * Defines a price bar with Open, High, Low, Close and Date encoded as number
3 */
4export type TPriceBar = {
5    date: number;
6    open: number;
7    high: number;
8    low: number;
9    close: number;
10    volume: number;
11};
12
13/**
14 * Parses JSON candles into TPriceBar array
15 * @param candles
16 */
17const parseCandles = (candles: any[]): TPriceBar[] => {
18    const priceBars: TPriceBar[] = [];
19
20    candles.forEach((candle: any) => {
21        const [timestamp, open, high, low, close, volume] = candle;
22        const openValue = parseFloat(open);
23        const highValue = parseFloat(high);
24        const lowValue = parseFloat(low);
25        const closeValue = parseFloat(close);
26        const volumeValue = parseFloat(volume);
27
28        priceBars.push({
29            date: timestamp / 1000,
30            open: openValue,
31            high: highValue,
32            low: lowValue,
33            close: closeValue,
34            volume: volumeValue,
35        });
36    });
37
38    return priceBars;
39};
40
41/**
42 * Fetches candles from Binance Rest API
43 */
44const getCandles = async (
45    symbol: string,
46    interval: string,
47    startTime?: Date,
48    endTime?: Date,
49    limit: number = 500,
50    binanceDomain = "us"
51): Promise<TPriceBar[]> => {
52    let url = `https://api.binance.${binanceDomain}/api/v3/klines?symbol=${symbol}&interval=${interval}`;
53    if (startTime) {
54        url += `&startTime=${startTime.getTime()}`;
55    }
56    if (endTime) {
57        url += `&endTime=${endTime.getTime()}`;
58    }
59    if (limit) {
60        url += `&limit=${limit}`;
61    }
62    try {
63        console.log(`SimpleBinanceClient: Fetching ${symbol} ${interval} from ${startTime} to ${endTime}`);
64        const response = await fetch(url);
65        const data = await response.json();
66        return parseCandles(data);
67    } catch (err) {
68        console.error(err);
69        return [];
70    }
71};
72
73export const simpleBinanceRestClient = {
74    getCandles,
75};
76