The javaScript var keyword is used to declare an implicit type variable, that specifies the type of a variable based on the initial value.
var varibale_name = value; Using var statement you can declare a function-scoped or globally-scoped variable, optionally initializing it to a value. If you want your code to run in an older browser, you must use var, don’t use of let and const.
JavaScript var keyword
A simple example code variable declared with the var keyword can be re-declared and updated in the same scope. var is the keyword that tells JavaScript you’re declaring a variable.
<!DOCTYPE html>
<html>
<body>
<script>
function varGreeter(){
var a = 10;
var a = 20;
console.log("New value of Var variable",a);
}
varGreeter();
</script>
</body>
</html>
Output:
Naming variables
Variable names are pretty flexible as long as you follow a few rules:
- Start them with a letter, underscore _, or dollar sign $.
- After the first letter, you can use numbers, as well as letters, underscores, or dollar signs.
- Don’t use any of JavaScript’s reserved keywords.
With that in mind, here are valid variable names:
var camelCase = "lowercase word, then uppercase";
var dinner2Go = "pizza";
var I_AM_HUNGRY = true;
var _Hello_ = "what a nice greeting"
var $_$ = "money eyes";And here are some invalid variable names:-
var total% = 78;
var 2fast2catch = "bold claim";
var function = false;
var class = "easy";Here’s a tabular representation highlighting the key differences between var, let, and const in JavaScript:
| Characteristic | var | let | const |
|---|---|---|---|
| Scope | Function-scoped | Block-scoped | Block-scoped |
| Hoisting | Hoisted and initialized with undefined | Hoisted but not initialized | Hoisted but not initialized |
| Redeclaration | Allowed | Allowed | Not allowed |
| Reassignment | Allowed | Allowed | Not allowed (constant) |
| Block-level scope | No | Yes | Yes |
Do comment if you have any doubts or suggestions on this JS var code.
Note: The All JS Examples codes are tested on the Firefox browser and the Chrome browser.
OS: Windows 10
Code: HTML 5 Version