About
A function declaration is one of the several grammar syntax that permits to define a function.
The execution of a function declaration can be done before the function declaration definition.
This is not the case with a function expression.
A function declaration defines a function and binds it to a variable in the current scope.
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Syntax
- The function name is mandatory.
- The function declaration cannot be written inside a code block that is not a declaration function
function name([param,[, param,[..., param]]]) {
[statements]
}
Function Execution Context
As every function, a function declaration follows the context principle.
// The global context
function globalFunction() {
// Inside another function
function innerFunction() {}
}
Example
At the top level of a program, the below declaration would create a global function called add.
/* The execution of a function declaration can be done before the function declaration definition */
/* This is not the case with a function expression */
console.log(add(2,3));
/* The function declaration definition */
function add(a,b) {
return a+b;
};
console.log(add);