Uses the SubtleCrypto interface of the Web Cryptography API to hash a message using SHA-256.

crypto-sha.js

/**
 * Returns SHA-256 hash from supplied message.
 *
 * @param   {String} message.
 * @returns {String} hash as hex string.
 *
 * @example
 *   sha256('abc').then(hash => console.log(hash));
 *   const hash = await sha256('abc');
 */
async function sha256(message) {
    const msgUint8 = new TextEncoder().encode(message);                           // encode as (utf-8) Uint8Array
    const hashBuffer = await crypto.subtle.digest('SHA-256', msgUint8);           // hash the message
    const hashArray = Array.from(new Uint8Array(hashBuffer));                     // convert buffer to byte array
    const hashHex = hashArray.map(b => b.toString(16).padStart(2, '0')).join(''); // convert bytes to hex string
    return hashHex;
}

Note that access to the WebCrypto API is restricted to secure origins (e.g. https).

How to use this algorithm as the signature in (Razorpay )payment gateway integration?

I'm not familiar with Razorpay, but checking it quickly, I suspect what you require may be for payment verification? If so, I think you would probably need crypto.subtle.sign for an HMAC signature using SHA-256, but I've not had occasion to use that, so I can't really help.