A long time ago, I saw someone encapsulate their entire JavaScript block with code something like the code below:
(function() {
// ...
})(this);
Questions:
Yes, that's correct. It's called a self invoking anonymous function expression.
JavaScript variables have either function scope, or global scope. There is no block scope. Enclosing your code in a self invoking function like the one in your example creates a temporary local scope for single-use, immediately-run code, without polluting the global namespace.
Consider the following:
<html>
<body>
...
<script>
(function() {
var x = '';
function myFunction () {
alert('Hello: ' + x);
}
x = 'Bob';
myFunction();
alert(typeof x); // string
alert(typeof myFunction); // function
})();
alert(typeof x); // undefined
alert(typeof myFunction); // undefined
</script>
<script src=other-javascript.js></script>
</body>
</html>
Whatever you declare in that self invoking function is held in a separate scope. The variable x and the function myFunction() cannot be accessed from anywhere else. The code in other-javascript.js won't see them, for example, and it would be free to declare another function myFunction() without conflicts.
