Google Apps Script SHA 1

hmac_sha1.gs

function hmac_sha() {
  var text = "I am SHA";
  var key = "hello";
  
  var hmacObject = Utilities.computeHmacSignature(Utilities.MacAlgorithm.HMAC_SHA_1, text, key);
  var txtHash = "";
  
  for (i = 0; i < hmacObject.length; i++) {
	 var hashVal = hmacObject[i];
	 if (hashVal < 0) {
		hashVal += 256;
	 }
	 if (hashVal.toString(16).length == 1) {
		txtHash += '0';
	 }
	 txtHash += hashVal.toString(16);
  }
  Logger.log(txtHash);
}

sha.gs

function toSHA1() {
  var text = "I am SHA Text or Something";
  var rawHash = Utilities.computeDigest(Utilities.DigestAlgorithm.SHA_1, text);
  var txtHash = "";
  
  for (i = 0; i < rawHash.length; i++) {
	 var hashVal = rawHash[i];
	 if (hashVal < 0) {
		hashVal += 256;
	 }
	 if (hashVal.toString(16).length == 1) {
		txtHash += '0';
	 }
	 txtHash += hashVal.toString(16);
  }
  return txtHash;
}

do you decryption techniques for sha?

Better : Utilities.computeDigest(Utilities.DigestAlgorithm.SHA_1, input, Utilities.Charset.UTF_8);