I need to know the difference between:
Namespace = (function () {
return {
name: 'Module',
dep: ['d', 'a']
};
})();
and
var Namespace = (function () {
return {
name: 'Module',
dep: ['d', 'a']
};
})();
simple as that but i still don't understand.
Personally, I never omit it. If you leave off the the var keyword that variable becomes a global one if the variable is declared inside a function. This is because variables have function level scope in JavaScript. In the example you have given Namespace will be a global variable whether you use var or not because it is not declared inside of a function. You can test this theory out by adding var to the Namespace variable in example 1 below.
Example 1:
//I am a global variable with or without the var keyword because
//I am declared outside of a function.
Namespace = (function () {
return {
name: 'Module',
dep: ['d', 'a']
};
})();
function test(){
Namespace = "I was changed because i have global scope";
}
//Run the test function to gain access to the global variable inside.
test();
//You will see that the value was changed by calling the test function
console.log(Namespace);
Now if you put your Namespace variable inside a function as it is now it will still be a global variable without the var keyword. In the example below I have moved your Namespace variable inside of function added the var keyword to it to make it a non global function. If you remove the var keyword from the Namespace variable inside of the function in example 2 you will see that it will then be a global variable and the last console.log(Namespace) call in the script will print out the Namespace value from the getNameSpace function.
Example 2:
function getNameSpace(){
var Namespace = (function () {
return {
name: 'Module',
dep: ['d', 'a']
};
})();
}
function test(){
Namespace = "I have global scope even inside a function because I am missing the var keyword.";
}
test();
//print the value of the global variable Namespace
console.log(Namespace);
//call get nameSpace
getNameSpace();
//This will still print the value from the test function because the variable inside of
//get Namespace has local or function level scope because it has the var keyword.
console.log(Namespace);
Hopefully all this makes more sense now. If it doesn't let me know I will try and help. A good thing to remember is to always use the var keyword and if you don't want another part of a script to access the variable directly then put it inside of function(also known as a closure).
When you use var you create a variable in the current scope of the function. Without var the variable will be created on the global scope which is usually bad.
Use var and always create your variables in a closed scope (which is not the global scope) unless you have a good reason not to do it.
