Binding Node.js

Binding Node.js code is just as easy as binding JavaScript. Let's see an example: suppose we have written a function called calcMD5 in a Node.js file called test.nodejs. The function accepts a string and returns its MD5 hash value. The test.nodejs file contains the following code:

/** test.nodejs */
var crypto = require('crypto');
/**
 * Calculates the MD5 hash value of a string.
 * @register {string -> string}
 */
var calcMD5 = function(str){
    return crypto.createHash('md5').update(str).digest('hex');
}

As we can see from the preceding code, we bind Node.js in the same manner that we previously used to bind the client-side JavaScript code. We also invoke it in the same way:

/** 603.opa */
md5 = %%test.calcMD5%%("Hello Opa!");
println("MD5 value: {md5}");

And finally, we compile and run the application:

opa test.nodejs 603.opa --

The result is as shown in the following screenshot: