How to declare global variables when using the strict mode pragma

Question

It\'s considered good practice to use a self-invoking function to wrap strict mode compliant code, often called the strict mode pragma:

(function(){
  \"use stri         


        

Answer 1

Benefit of alt 2 and 3 is that they keep all of the code inside the "container function." One line of code outside of the function is easy to miss when reading the code.

Also:

• "GLOB" should be the application's name. -- You want to allow for more than one application per html/js file without name collisions.

Answer 2

Andrea Giammarchi has a nice technique for doing this, that works across browsers. Define a function in your self-invoking function called globalEval like so:

(function () {
    "use strict";
    function globalEval(data) {
        data = data.replace(/^\s*|\s*$/g, "");
        if (data) {
            var head = document.getElementsByTagName("head")[0] || document.documentElement,
                script = document.createElement("script");
            script.type = "text/javascript";
            script.text = data;
            head.appendChild(script);
            head.removeChild(script);
        }
    }

    // use globalEval to stick variables into the global scope
    globalEval("var myGlobal = 1;");
    // myGlobal === 1
)();
// myGlobal === 1

Or define the globalEval function outside of the self-invoking code if you want to use it in other scopes.

Answer 3

IMO alternative 3 is best. But it assumes that window represents the global scope - which is true for the browser but not for other JS environments (command line, Node.js, etc.).

The following will work across the board:

(function(globals){
  "use strict";
  globals.GLOB = {};
}(this));

Answer 4

Method 1 would fail if it's pasted in another function.

Using method 3, it is easier to export your methods to another namespace. Simply replacing window with, say, frames[0] or document is enough to attach all methods to a custom namespace.

I recommend method 3, for the last reason.

Answer 5

I know this is an old question but there's one not mentioned way of getting global context:

(function(globals){
  "use strict";
  globals.GLOB = {};
}( (1,eval)('this') ));

(1,eval)('this')

will evaluate this from global context, so you can paste this wherever you like and you will always get global context