# Javascript variable declaration

# Declaring a variable in JS
Well, there is a thing that always confused me; which method should we use to declare a variable 😵?

Well, if you are like me, then get ready to dive deep!

## var

`var` was introduced in the earliest version of Javascript, and you will find it in legacy codebases (also in Stack Overflow answers 😜).

You might be thinking, "Then what is the problem with it?"

The first problem is **re-declaration**

In `var` you can not only reassign the variable but also re-declare it. 

Here's an example:
```javascript
var time = "4pm";
time = "5pm"; // re-assignment
var time = "8pm"; // re-declaration
```
You may be thinking "Hey! What's the problem with that?" Let me tell you a straightforward answer :- Re-declaring does nothing but induces 🐛. Creepy ones😱.

The second problem is its **Scope**

`var` has a global scope(except when it's in a function), which means it can be used anywhere in the code. See this code:
```javascript
var day = "Wednesday";
if (40 > 3) {
   var day = "Monday";
}
```

In this code, you will think that you made a new variable day, but didn't notice it was assigned before. This can cause many bugs so in ES6, `let` and `const` were introduced.

## let

You can think of `let` as the ES6 version of `var`. You can do similar things, but it fixes the problems.

The first problem fixed is that you cannot **re-declare** a variable.

For a demo, see this:
```javascript
let time = "4pm";
// re-assignment works
time = "5pm";
// re-declaration throws an error
let time = "8pm"; //does not work
```
The second problem fixed is that `let`, when defined in a code block, has a scope of only that block.

## const

`const` should be your way of assigning variables all the time when you know the value should not change. It is similar to `let`, but its value is constant.

## Conclusion

Always use `const` as default, and when you know the value would be changed in the future, use `let`. Never use `var` as it will induce bugs in your code.

### A quick note

This is my first blog, so if it has any errors, please tell me 😊.
**THANKS FOR READING !!!**