Compute base64 SHA-256 hash in browser

base64SHA256Hash.js

const hash = message => {
    return new Promise((resolve, reject) => {
        const msgBuffer = new TextEncoder().encode(message);                    
        crypto.subtle.digest('SHA-256', msgBuffer)
        .then(hashBuffer => {
            const hashArray = Array.from(new Uint8Array(hashBuffer));
            const hexString = hashArray.map(b => b.toString(16).padStart(2, '0')).join('');
            const str = hexString
                .replace(/\r|\n/g, "")
                .replace(/([\da-fA-F]{2}) ?/g, "0x$1 ")
                .replace(/ +$/, "")
                .split(" ");
            const b64 = btoa(String.fromCharCode.apply(null, str)); // Polyfill may be required
            resolve(b64);
        })
        .catch(reject);
    });