Skip to main content

JavaScript Basic: Five Primitive Data Types You Must Know

JavaScript (JS) is a programming language which can add logic and interactivity to a page. If we treat HTML as a noun and treat CSS as a adjective in a sentence, we can treat JS as a verb which is the one to take action.

Today, I learned five primitive datatypes about JS.

Numbers

Numbers are very simple, just like 4, 10, -29.etc

It can do some math. For example we type a simple math in the console (open any web page on Google Chrome, right click and inspect the page, click "console" next to the "Element" bar):



I type "4+26" and the result is calculated automatically.

The JS follows the order of operations that all regular math follows as well. For example, (3+5)*8=8*8=64.

Besides simple math, JS can also do modulo which is a reminder operator. It has "%" sign between two numbers. For example:


The result shows when 10 divide 3, the reminder is 1 (3*3+1=10).

Strings


  • They can be text inside single or double quotes
For example "Hello world"
  • They can be concatenation
  • They can escape characters start with "\"
Pay attention: we need to have a double quote for the whole text, and "\" between the inside double quote text.
  • They have a length property
Basically, it counts how many characters in the text. 


  • They can access individual characters by using [] and an index. 

The third character of "hello" is "l".

Variables (Booleans)

Variables are simple containers that store values. They follow this pattern:

Var your variableName = yourValue;

  • They can store all of the values we've seen
For example:

var name = "Lilly";
var number = 20;
                      
  • They can recall the stored value by calling the variable name

Once we type our first var name "Lilly" in the JS, it already store the data. When we type "name", it will recall the data "Lilly".

So does the number, too. Since the JS has stored the number "20", when we use number to do the simple math, it will apply the number in the math operation.

  • We can also update existing variables
When we update a new name "Kitty", JS will also update the existing name "Lilly".


Null 

Null is "explicitly nothing". Null expresses a lack of identification, indicating that a variable points to no object. (From MDN)


Undefined

Undefined refers to variables that are declared but not initialized.

Since we don't give any value of those variables, the result is undefined.



Labels:

Comments

Post a Comment

Popular posts from this blog

GIT Study Note: Six Git Commands You Should Know!

What is Git? According to Git website , Git is a free and open source distributed version control system designed to handle everything from small to very large projects with speed and efficiency. Basically, we can use Git to track all of changes and revert them back if we made mistakes. The version control system is a way for us to work with different versions of our code, so that we can save different features and make notes as we progress. It is also very useful for team collaboration. Six Git Command You Should Know 1. Git Init In our server, we need to create a "Git" directory and inside of "Git", we make another direcory "git_inro". Then, we add a file "app,js" in the "git_intro" folder. The first thing we need to run is "git init" . When we run git init, it will make a directory which is hidden called ".git". Wherever I run that git init command, it's going to track all of our changes. ...
Post a Comment
Read more

Intro To Authentication: Three Useful Tools Will Make Everything Easier

Authentication is very important for both users and websites. It helps to keep users' information safe and also helps us to manage the accounts. Authentication is also complex because there is a lot of moving pieces that have to fit together in just the right way to make that work. The course introduce three tools to make authentication more quickly and safely. 1. Passport.js Passport.js will make our life easier and make our code shorter. It also helps to make implementation faster. Most importantly, it is used a lot in the real word. 2. Passport Local Passport Local is for username and password. It's about providing this entry point into all sorts of destinations. 3. Passport Local Mongoose This package will help us implement authentication with passport, and it's specially made to work with mongoose. We are also going to use these three tools into a Secret Page App project, which will show in next few posts.
Post a Comment
Read more

Express Study Notes: Five Steps To Develop My First Express App

In the last post, I shared my study note about one of the most important reason that Node is very popular is because Node has the largest package ecosystem of open source libraries in the world. Node's NPM, the package manager for Javascript, contains almost 200,000 packages which are centralized on the NPM website. And more importantly, NPM has a command line tool which help us to install packages really easily. The course instructor told us that we are going to learn Express.js to develop Apps in this course. screenshot for the Express.js.com homepage What is Express.js? Express.js is a web development framework. According to the course, framework is a bunch of code that someone else wrote just like a library is except when we use a framework, we have less control. The goal of using this framework is to make our development of APPs faster. Why do we use Express.js? 1. It is the most popular Node web development framework so far. 2. It is a very lightweight ...
Post a Comment
Read more