A JavaScript variable is a named container used to store data values. Variables allow you to store information that can be referenced and manipulated within your program.
JavaScript variable Syntax
(typeOfVariable) variableName = variableValue
Define a variable:- in the below example, variableName name assigned value John
var name="John";
Using a variable:- Now, You can use variable name in the file.
console.log(name); //John
Note:- If you did not define the variable type then it will work as like var variable,
name="John";
console.log(name); //John
There are two types of JavaScript variable
1) local variable
2) Global variable
1) Local variable:- A variables declared in a function, become LOCAL variable to the function. Local variables have Function scope: They can only be accessed from within the function.
function user() {
var name = "John";
console.log(name);
}
user();
console.log(name);
Note:- When we call console.log(name) after the function user() call then output will be blank.
2) Global Variables:- A variable declared outside a function, becomes GLOBAL variable. A global variable has global scope: All scripts and functions on a web page can access it.
var name = "John";
function myFunction() {
console.log(name)
}
Javascript Variable – Interview Questions
Q 1: What is a variable?
Ans: A container for storing data values.
Q 2: How do you create a variable?
Ans: Using var, let, or const.
Q 3: Can variable values change?
Ans: Yes, except const.
Q 4: Are variables case-sensitive?
Ans: Yes.
Q 5: Can a variable start with a number?
Ans: No.
Javascript Variable – Objective Questions (MCQs)
Q1. Variables are used to ______.
Q2. Which keyword is used to declare a variable?
Q3. Variable names must start with ______.
Q4. Which is a valid variable name?
Q5. JavaScript variables are ______ typed.