function declaration - Land of code

A function declaration is one way of creating a function in JavaScript.

A function declaration is defined by using the function keyword, followed by a name, followed by parenthesis and then curly braces:

function name() {
 statement(s);
}

Between the curly braces is where you write your statement(s). Between the parenthesis you can specify parameter(s):

function calSqrArea(length, width) {
 return length * width;
}

To be used, it must be invoked, by using its name:

name();

You can add any required parameter(s);

console.log(calcSqrArea(5, 3));

A function declaration must start with the function keyword and be given a name.

You can call a function declaration before you define it! This works because of a process called hoisting. In JavaScript, hoisting is a behaviour which moves all declarations to the top of the code, before execution.

A function that is created with a function declaration is a function object that has all of the properties, methods and behaviour of function objects.

By default, functions return undefined. To return any other value, the function must have a return statement that specifies the value to return.

conclusion

In JavaScript there’s more than one way to create a function. You should choose a function declaration when you want to create a function with global scope, so it’s available throughout your code.