Functions

A function is a stored set of statements that perform some tasks or does some computation and then return the result to the user. Once stored the function can then be called whenever it is needed instead of rewriting all those statements. It can also be set to take input values.

The idea is to put some commonly or repeatedly done tasks together and make a function so that instead of writing the same code again and again for different inputs, we can call that function.

JavaScript has many built-in functions that we can call to perform certain tasks. We can also create our own user-defined functions in JavaScript using the keyword function. This is the basic syntax to create a function in JavaScript:


function functionName(inputParameter1, inputParameter2, ...) { 
    //function statements
}

Example


//this function doubles the input value                
function doubleNumber(number) {
    return number * 2;
}

//here we call the function
console.log(doubleNumber(10));  //outputs 20

Javascript has many built-in function for performing various tasks

Here are some common built-in functions:

charAt() - returns a character in a string at the given index
indexOf() - returns the index of a the first occurrence of a character in a string
charCodeAt() - returns the ascii number of the character at the given index in a string
fromCharCode() - returns the character of the given ascii number
replace() - replaces a matched substring with a new substring
split() - splits a string into an array of substrings
toUpperCase() - returns the given string all in upper case
toLowerCase() - returns the given string in all lower case
join() - opposite of split(). Joins all array elements into a string
pow() - returns a base to the exponent power
min() - returns the smallest valued element
max() - returns the largest value element
round() - returns a number rounded to the nearest integer

Exercise

Create a function called 'add' that adds 2 numbers and returns the result.


 add(num1, num2) {
    let result = num1   ;
    return ();
}

  try Again!