use sha 256 in js code example

Example: sha256 javascript

async function sha256(message) {
    // encode as UTF-8
    const msgBuffer = new TextEncoder().encode(message);                    
    // hash the message
    const hashBuffer = await crypto.subtle.digest('SHA-256', msgBuffer);
    // convert ArrayBuffer to Array
    const hashArray = Array.from(new Uint8Array(hashBuffer));
    // convert bytes to hex string                  
    const hashHex = hashArray.map(b => ('00' + b.toString(16)).slice(-2)).join('');
    return hashHex;
}