Functions in Javascript

A JavaScript function is a block of code designed to perform a particular task.

• Function Definition - Before we use a function, we need to define it. A function definition (function declaration or function statement) consists of the function keyword, followed by: - The function's name.- A list of parameters to the function, enclosed in parentheses and separated by commas. - The JavaScript statements that define the function, enclosed in curly brackets {...}.
• Calling functions - Defining a function does not execute it. A JavaScript function is executed when "something" invokes it (calls it).

// function definition 
function sum(){
  var a = 10, b = 40;
  var total = a+b;
  console.log(total);
}
sum(); // calling function        

Output: 50        

Function Parameter & Function Arguments:

• Function parameters are the names listed in the function's definition.
• Function arguments are the real values passed to the function.

// a and b is parameter
function sum(a,b){
var total = a+b;
console.log(total);
}
sum(20,30); // argument is 20 and 30
sum(50,50); // argument is 50 and 50        

Output: 50
        100        

Why to use functions?

A function is a group of reusable code that can be called anywhere in your program. This eliminates the need to write the same code again and again.

Good coding practice follows DRY => Do not repeat yourself so we use functions.

Function expressions

Function expressions simply mean to create a function and put it into the variable.

function sum(a,b){
var total = a+b;
console.log(total);
}
var funExp = sum(5,15);        

Output: 20        

return keyword

When JavaScript reaches a return statement, the function will stop executing. Functions often compute a return value. The return value is "returned" back to the "caller".

function sum(a,b){
  return total = a+b;
}
var funExp = sum(5,25);
console.log('the sum of two no is ' + funExp );        

output: the sum of two no is 30        

Anonymous Function

A function expression is similar to and has the same syntax as a function declaration. One can define "named" function expressions (where the name of the expression might be used in the call stack for example) or "anonymous" function expressions.

var funExp = function(a,b){
  return total = a+b;
}
var sum = funExp(15,15);
var sum1 = funExp(20,15);
console.log(sum > sum1 );        

Output: false        

By delving into the depths of functions in JavaScript, you've embraced the essence of what it means to be a curious and passionate learner. Your eagerness to expand your knowledge and understanding fuels our own enthusiasm for sharing insights and discoveries with you

Happy Testing ??