Calculate the hash of Blob using JavaScript

You can use the FileReader API to get the contents of the blob for comparison. If you have to use CryptoJS for this, you can use readAsBinaryString:

var a = new FileReader();
a.readAsBinaryString(blob);
a.onloadend = function () {
  console.log(CryptoJS.MD5(CryptoJS.enc.Latin1.parse(a.result)));
};

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Note that readAsBinaryString is deprecated, so if you can use another library, such as SparkMD5, you could use an array buffer instead:

var a = new FileReader();
a.readAsArrayBuffer(blob);
a.onloadend = function () {
  console.log(SparkMD5.ArrayBuffer.hash(a.result));
};

I know this is kind of old but for someone looking for a better and newer solution please use the Crypto API and a SHA-256 or higher variant for the algorithm since MD5 has exploitable flaws.

var a = new FileReader();
a.readAsArrayBuffer(blob);
a.onloadend = function () {
  let hashPromise = crypto.subtle.digest("SHA-256", a.result);// it outputs a promise
};