Function in java script

Function definition

function msg(){
console.log("Hello, welcome to capscom technology.");
}

Function call

msg()

Parametrised function

function sum(a, b){
return a+b;
}
console.log( sum(100, 200) );

Default parameters 

function doLogin(user="Guest"){
console.log("Login with "+user);
}
doLogin();
doLogin("Aman");