I thought one of the point of functions in javascript was to provide scope. Things defined in a function were only available inside the function.
function cat(name) {
talk = function() {
alert(" say meeow!" )
}
}
talk()
I would expect the above code to fall over because talk should not be visible. But it is, why?
It is because you didn't declare it with a var keyword.
If you don't use the var keyword, it will be in the global scope. If you do use var, it will be in the function scope:
function cat(name) {
//anonymous function assigned to the local variable talk
var talk = function() {
alert(" say meeow!" )
};
}
You can declare named functions without the var keyword, and they will still be in the local scope:
function cat(name) {
//local talk function
function talk() {
alert(" say meeow!" )
};
}
You haven't actually defined the variable in any scope. So it default to global scope.
function cat(name) {
var talk = function() { // <-- added var
alert(" say meeow!" )
}
}
talk() // fail
JavaScript allows you to use variables without defining them, this makes the programming language easier to learn and more flexible. I wouldn't recommend you make use of this feature though. Always define your variables.
inside of a function, you have to declare variables with "var" or they are declared globally. so you would do:
function cat(name) {
var talk = function() {
alert(" say meeow!" )
}
}
talk() // error: undefined
