How to Create, Read, Update, & Delete Cookies in JavaScript

How to Create, Read, Update, & Delete Cookies in JavaScript

JavaScript – What are Cookies ? – Today you will learn about javaScript cookies and it’s features like, how to create cookies, how to delete cookies, how to change cookies, how to get all javaScript cookies, How to read javaScript cookies, how to set cookies.

JavaScript – What are Cookies ? – Today you will learn about javaScript cookies and it’s features like, how to create cookies, how to delete cookies, how to change cookies, how to get all javaScript cookies, How to read javaScript cookies, how to set cookies.

What are cookies ?

Basically JavaScript cookies are data. Cookies are use for stored users information for web pages. Small data text files cookies are store in your computer are cookies.

When a user requests a web page from a web server using a web browser. After that the web server sends a web page and the web server forgets everything about the user. To remember users’ information, cookies are use. Cookies are save in name-value pairs.

JavaScript Cookies

Contents

  • Create a Cookie with JavaScript
  • Read a Cookie with JavaScript
  • Change a Cookie with JavaScript
  • Delete a Cookie with JavaScript
  • Set a Cookie Function
  • Get a Cookie Function
  • Check a Cookie Function
  • Check Program

Create a Cookie with JavaScript

JavaScript can create, change, read, and delete cookies using the document.cookie property.

This example shows – how to create cookies in JavaScript.

Example
document.cookie = "username=John Doe";

By default, the cookie is delete. When the user browser is close. You want to save with specific time. You can set the end date (in UTC time).

document.cookie = "username=John Doe; expires=Thu, 24 Jan 2019 12:00:00 UTC";

Read a Cookie with JavaScript

This example shows how to read cookies.

Example
var xyz = document.cookie;

Change a Cookie with JavaScript

You can change a javaScript Cookie the same way as you create it.

Example
document.cookie = "username=John Smith; expires=Thu, 24 Jan 2019 12:00:00 UTC; path=/";

Delete a Cookie with JavaScript

If you want to delete a cookie. Set Cookies expiry date from the past.

Example
document.cookie = "username=; expires=Thu, 01 Jan 1970 00:00:00 UTC; path=/;";

Set a Cookie Function

In This javascript set cookie example, you will learn how to create cookies with javascript cookies

Example
function setCookie(cname, cvalue, exdays) {
  var d = new Date();
  d.setTime(d.getTime() + (exdays*24*60*60*1000));
  var expires = "expires="+ d.toUTCString();
  document.cookie = cname + "=" + cvalue + ";" + expires + ";path=/";
}

The above example, these are the following params means :

  • cname => cookie name
  • cvalue => cookiee value
  • exdays => expires time of cookie

Get a Cookie Function

we need to create a function that returns the value of a specified cookie. A function that returns a value of a cookie is created. It takes the cookie name as a parameter (cname).

Example
function getCookie(cname) {
  var name = cname + "=";
  var decodedCookie = decodeURIComponent(document.cookie);
  var ca = decodedCookie.split(';');
  for(var i = 0; i <ca.length; i++) {
    var c = ca[i];
    while (c.charAt(0) == ' ') {
      c = c.substring(1);
    }
    if (c.indexOf(name) == 0) {
      return c.substring(name.length, c.length);
    }
  }
  return "";
}

Check a Cookie Function

Now, we will create the check cookie function that checks if a cookie is exist or not. The cookie is set. It will display it otherwise, it will display a prompt box and asking for the name of the user, and stores the username cookie for 100 days, by using the setCookie javascript function.

Example
function checkCookie() {
   var username = getCookie("username");
   if (username != "") {
    alert("Welcome again " + username);
   } else {
     username = prompt("Please enter your name:", "");
     if (username != "" && username != null) {
       setCookie("username", username, 100);
     }
   }
 }

Check Program with preview

<!DOCTYPE html>
<html>
<head>
<title>JavaScript Cookies Example</title>
</head>
 
<body onload="checkCookie()"> 
</body>
<script>
function setCookie(cname, cvalue, exdays) {
var d = new Date();
d.setTime(d.getTime() + (exdays*24*60*60*1000));
var expires = "expires="+ d.toUTCString();
document.cookie = cname + "=" + cvalue + ";" + expires + ";path=/";
}
function getCookie(cname) {
var name = cname + "=";
var decodedCookie = decodeURIComponent(document.cookie);
var ca = decodedCookie.split(';');
for(var i = 0; i <ca.length; i++) {
var c = ca[i];
while (c.charAt(0) == ' ') {
c = c.substring(1);
}
if (c.indexOf(name) == 0) {
return c.substring(name.length, c.length);
}
}
return "";
}
function checkCookie() {
var username = getCookie("username");
if (username != "") {
alert("Welcome again " + username);
} else {
username = prompt("Please enter your name:", "");
if (username != "" &amp;&amp; username != null) {
setCookie("username", username, 100);
}
}
}
</script>
</html>

Programming a Javascript Simon Game Tutorial

Programming a Javascript Simon Game Tutorial

In this javascript tutorial, I recorded myself live programming an html5 javascript simon game.

In this javascript tutorial, I recorded myself live programming an html5 javascript simon game.

For those who don't know, I'm a full stack web developer who has been in the industry for over 5 years now. There is a lot of things I have learned along the way and I'd like to share that knowledge with anyone wanting to learn!

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Understanding Memoization And Dynamic Programming in Javascript

Understanding Memoization And Dynamic Programming in Javascript

In this Javascript tutorial I will explain what memoization is, how to use it, when you should use memoization, how to use memoization, what dynamic programming is, how to use memoization in dynamic programming. Memoization is a big complicated word that you may have never even heard before, but you may be surprised to know that you are most likely already using memoization without even realizing it.

Memoization is a big complicated word that you may have never even heard before, but you may be surprised to know that you are most likely already using memoization without even realizing it. Memoization is just the act of caching values so that they can be calculated quicker in the future. Memoization is really useful in all parts of programming, but where it is most useful is in dynamic programming. In this video I will explain what memoization is, how to use it, and why it is so useful especially in dynamic programming.

🧠 Concepts Covered:

  • What memoization is
  • When you should use memoization
  • How to use memoization
  • What dynamic programming is
  • How to use memoization in dynamic programming

JavaScript Tutorial: if-else Statement in JavaScript

JavaScript Tutorial: if-else Statement in JavaScript

This JavaScript tutorial is a step by step guide on JavaScript If Else Statements. Learn how to use If Else in javascript and also JavaScript If Else Statements. if-else Statement in JavaScript. JavaScript's conditional statements: if; if-else; nested-if; if-else-if. These statements allow you to control the flow of your program's execution based upon conditions known only during run time.

Decision Making in programming is similar to decision making in real life. In programming also we face some situations where we want a certain block of code to be executed when some condition is fulfilled.
A programming language uses control statements to control the flow of execution of the program based on certain conditions. These are used to cause the flow of execution to advance and branch based on changes to the state of a program.

JavaScript’s conditional statements:

  • if
  • if-else
  • nested-if
  • if-else-if

These statements allow you to control the flow of your program’s execution based upon conditions known only during run time.

  • if: if statement is the most simple decision making statement. It is used to decide whether a certain statement or block of statements will be executed or not i.e if a certain condition is true then a block of statement is executed otherwise not.
    Syntax:
if(condition) 
{
   // Statements to execute if
   // condition is true
}

Here, condition after evaluation will be either true or false. if statement accepts boolean values – if the value is true then it will execute the block of statements under it.
If we do not provide the curly braces ‘{‘ and ‘}’ after if( condition ) then by default if statement will consider the immediate one statement to be inside its block. For example,

if(condition)
   statement1;
   statement2;

// Here if the condition is true, if block 
// will consider only statement1 to be inside 
// its block.

Flow chart:

Example:

<script type = "text/javaScript"> 

// JavaScript program to illustrate If statement 

var i = 10; 

if (i > 15) 
document.write("10 is less than 15"); 

// This statement will be executed 
// as if considers one statement by default 
document.write("I am Not in if"); 

< /script> 

Output:

I am Not in if
  • if-else: The if statement alone tells us that if a condition is true it will execute a block of statements and if the condition is false it won’t. But what if we want to do something else if the condition is false. Here comes the else statement. We can use the else statement with if statement to execute a block of code when the condition is false.
    Syntax:
if (condition)
{
    // Executes this block if
    // condition is true
}
else
{
    // Executes this block if
    // condition is false
}


Example:

<script type = "text/javaScript"> 

// JavaScript program to illustrate If-else statement 

var i = 10; 

if (i < 15) 
document.write("10 is less than 15"); 
else
document.write("I am Not in if"); 

< /script> 

Output:

i is smaller than 15
  • nested-if A nested if is an if statement that is the target of another if or else. Nested if statements means an if statement inside an if statement. Yes, JavaScript allows us to nest if statements within if statements. i.e, we can place an if statement inside another if statement.
    Syntax:
if (condition1) 
{
   // Executes when condition1 is true
   if (condition2) 
   {
      // Executes when condition2 is true
   }
}

Example:

<script type = "text/javaScript"> 

// JavaScript program to illustrate nested-if statement 

var i = 10; 

if (i == 10) { 

// First if statement 
if (i < 15) 
	document.write("i is smaller than 15"); 

// Nested - if statement 
// Will only be executed if statement above 
// it is true 
if (i < 12) 
	document.write("i is smaller than 12 too"); 
else
	document.write("i is greater than 15"); 
} 
< /script> 

Output:

i is smaller than 15
i is smaller than 12 too
  • if-else-if ladder Here, a user can decide among multiple options.The if statements are executed from the top down. As soon as one of the conditions controlling the if is true, the statement associated with that if is executed, and the rest of the ladder is bypassed. If none of the conditions is true, then the final else statement will be executed.
if (condition)
    statement;
else if (condition)
    statement;
.
.
else
    statement;


Example:

<script type = "text/javaScript"> 
// JavaScript program to illustrate nested-if statement 

var i = 20; 

if (i == 10) 
document.wrte("i is 10"); 
else if (i == 15) 
document.wrte("i is 15"); 
else if (i == 20) 
document.wrte("i is 20"); 
else
document.wrte("i is not present"); 
< /script> 

Output:

i is 20