在函数中参考外部JavaScript文件

Question

Is it possible to reference a JavaScript file inside of a JavaScript function?

Therefore i am wanting to convert this:

<script type="text/javascript" src="http://crypto-js.googlecode.com/files/2.5.3-crypto-sha1-hmac.js"></script>
<script type="text/javascript">

var hmacString = Crypto.HMAC(Crypto.SHA1, "Message", "Secret Passphrase", { asString: true });

</script>

In to:

function hmac (input){

  var hmacString = Crypto.HMAC(Crypto.SHA1, "Message", "KEY", { asString: true });

  return hmacString;

}

I am using a tool called Cast Iron, which therefore restricts JavaScript down to only a function, but i need to call an external file, to load the needed functionality.

Is this even possible?

Answer 1

If I understand correctly, yes you can access functions and classes from one JS file as long as the other class was loaded before you attempt to access it.

So, if some-javascript-file.js has a function named getThings() , then you can do this:

<script type="text/javascript" src="http://cdn.example.com/js/some-javascript-file.js"></script>
<script type="text/javascript">
    var things = getThings(); // getThings is a publicly accessible function in an external class.
</script>

Answer 2

OK the screenshot kind of helps. It seems you want something from an external JS file, and to manipulate it inside this function.

So you could have one javascript file with:

var foo = 'foo'; //this is in the global scope

and then your other file has:

function hmac(key){
    alert(document.foo);
}

should access what you want

Answer 3

Yes, you can load other js files with javascript. Depending on the load state where your function is executed, you may either use

document.write('<script type="text/javascript" src="http://crypto-js.googlecode.com/files/2.5.3-crypto-sha1-hmac.js"'+'><'+'/script>"');
// loads synchronouly and executes
Crypto.HMAC(...); // is available here

Watch out that document.write breaks the whole page once your DOM is loaded. You can also use:

var s = document.createElement("script");
s.type = "text/javascript";
s.src = "http://crypto-js.googlecode.com/files/2.5.3-crypto-sha1-hmac.js";
s.onload = function() {
    // the file should be executed now so
    Crypto.HMAC(...); // is available here
};
document.head.appendChild(s); // load asychronously

See also Load js from external site on fly