After looking around, I'm still not too clear on this.
function() {
var a = 'foo';
a = 'bar';
}
I'm attempting to update the value of a variable here. Since the variable is already declared with "var", does my second line only update the variable, or does it also make it global?
It only updates the variable.
One use of var, anywhere in the function, will declare it to be a local variable.
When you assing a value to a variable javascript will check if that variable is defined within the current block/scope.
If yes then it will update that variable. If no then it will check its parent block. and this goes on until it finds a variable declared in the global space.
In your case it will update the var a inside your function.
If no variable is found in the global space it will create a new one and thus pollutes the global namespace.
It will update the variable value, not make it global. To make it global, declare it outside the function:
var a = 'foo';
function() {
a = 'bar';
}
Your second variable which is the 'bar' must be the new value now of a. Then, the scope for this is just for this function only and cannot work with other function or an outside call.
