Function

Functions are one of the fundamental building blocks in JavaScript.

And the purpose of Function is to execute a set of instruction when called.

Let's look at one.

function add(a, b) {
  return a + b;
}
const result = add(2, 5);
console.log(result);

Now there are few things to understand here, lets get it one by one.

• function: This is the keyword (reserved word) used to define.
• add: This is name of the function, it can be anything as long as they are valid identifier.
• (a, b): These can further be divided in 2 types
  • a, b: These are called parameters, here we have 2 of them separated by a ,. These are also know as inputs
  • (): All the parameters are wrapper by them.
• {}: These represent the body of the function. when the function is called, code withing these brackets will get executed.
• return: This is the keyword (reserved word) used to return data from the function. These are also known as outputs.
• add(2, 5): Lets break it down.
  • add: The name of the function which me want to call.
  • 2, 5: These are called arguments, and this denotes that a=2 and b=5.
  • (): All the arguments are wrapper by them.

Try removing the return keyword, and run the example.

In Javascript, functions can also be assigned to a variable. Lets check that out in code.

function add(a, b) {
  return a + b;
}
const alsoAdd = add;
const result = alsoAdd(2, 5);
console.log(result);

There are two things to note in the above code.

• Just like any other value, functions can also be assigned to a variable. And you call them using this variable name, as well as the old name.
• Remember just like objects, by assigning functions to a variable we are not copying it, instead just passing its reference.