Java Reference
In-Depth Information
If a function is defined using a function declaration, the whole function is hoisted to the top
of the function, meaning that it can be invoked before it has been defined.
A function expression (where an anonymous function is assigned to a variable) is hoisted
in a similar way to variables. So the declaration will be hoisted, but not the actual function.
This means that the function cannot be invoked until after it appears in the code.
This behaviour also applies to the global scope, as can be seen in the following example:
add(2,3); // this will work because the add function is
hoisted
function add(x,y){
console.log(x + y);
}
subtract(5,2); // this won't work because the subtract
function
↵
hasn't been defined yet
subtract = function(x,y){
console.log(x - y);
}
This is the major difference between the two ways of defining function literals and it may
influence your decision regarding which one to use. Some people like that using function
expressions means you're required to define all functions and assign them to variables pri-
or to using them. To avoid any problems, a ninja should either use function declarations
or ensure that all function expressions are defined at the top of the scope, along with any
variable declarations.
