I sometimes try to remember basis of JavaScript Functions. So, I often exercise about it. I followed this link https://www.w3schools.com/js/js_function_definition.asp. I copied some important descriptions from that link. My aim is to follow this post when I need to remember again 🙂
JavaScript Functions
A JavaScript function is a block of code designed to perform a particular task.
A Function is much the same as a Procedure or a Subroutine, in other programming languages.
Why Functions?
You can reuse code: Define the code once, and use it many times.
You can use the same code many times with different arguments, to produce different results.
JavaScript Function Syntax
Function parameters are listed inside the parentheses () in the function definition.
Function arguments are the values received by the function when it is invoked.
Inside the function, the arguments (the parameters) behave as local variables.
Function Declaration (function statement)
function name(parameter1, parameter2, parameter3) {
// code to be executed
}Function Expression
The function below is actually an anonymous function (a function without a name).
Functions stored in variables do not need function names. They are always invoked (called) using the variable name.
var x = function (a, b) {return a * b};
var z = x(4, 3);Function() Constructor
Functions can also be defined with a built-in JavaScript function constructor called Function().
var myFunction = new Function("a", "b", "return a * b");
var x = myFunction(4, 3);Self-Invoking Function (Immediately Invokable Function Expression IIFE)
When functions are used only once, a common pattern is an IIFE (Immediately Invokable Function Expression).
You have to add parentheses around the function to indicate that it is a function expression:
The function below is actually an anonymous self-invoking function (function without name).
(function () {
var x = "Hello!!"; // I will invoke myself
})();