Getting TypeError: this is not a typed array using Buffer.from in mocha

I also got the same error. You can try this

var b = new Buffer('some string or other');

Second param is encoding (optional). By default encoding will be utf-8

You might be using an old version of Node.js.

Buffer.from was introduced in version 6.0.0:

To make the creation of Buffer objects more reliable and less error prone, the various forms of the new Buffer() constructor have been deprecated and replaced by separate Buffer.from(), Buffer.alloc(), and Buffer.allocUnsafe() methods.

There's no reference to this method in previous versions of documentiation.

You could either update to 6.0.0 or use a deprecated constructor API, which has the following signature:

new Buffer(str[, encoding])