JavaScript var
Last Updated :
09 Apr, 2024
The JavaScript var statement declares variables with function scope or globally. Before ES6, var was the sole keyword for variable declaration, without block scope, unlike let and const.
Syntax:
var variableName = valueOfVar;
Function Scope
The variables declared inside a function are function-scoped and cannot be accessed outside the function.
The variables declared using the var statement are hoisted at the top and are initialized before the execution of code with a default value of undefined. The variables declared in the global scope that is outside any function cannot be deleted
Examples of JavaScript var
Example 1: In this example, we will declare a global variable and access it anywhere inside the program
Javascript
var test = 12
function foo(){
console.log(test);
}
foo();
Output:
12
Example 2: In this example, we will declare multiple variables in a single statement
Javascript
var test1 = 12,
test2= 14,
test3 = 16
function foo(){
console.log(test1, test2, test3);
}
foo();
Output:
12 14 16
Example 3: In this example, we will see the hoisting of variables declared using var
Javascript
console.log(test);
var test = 12;
Output:
undefined
Explanation: We get the output without any error because the variable test is hoisted at the top even before the execution of the program began and the variable is initialized with a default value of undefined
Example 4: In this example, we will redeclare a variable in the same global block
Javascript
var test = 12;
var test = 100;
console.log(test);
Output:
100
Explanation: We did not get any error when redeclaring the variable if we did the same with the let keyword an error would be thrown
Example 5: In this example, we will redeclare the variable in another scope and see how it is the original variable.
Javascript
var test = 12;
function foo(){
var test = 100;
console.log(test);
}
foo();
console.log(test);
Output:
100
12
Explanation: We did not get any error while redeclaring the variable inside another function scope and the original value of the variable is preserved.
Example 6: In this example, we will try to delete a global variable declared using var in the ‘use strict’ mode
Javascript
'use strict';
var test = 12;
delete(test);
console.log(test);
Output:
Explanation: Whenever a variable is declared using var in global scope it cannot be configured. Hence it cannot be deleted using the delete keyword. and an error is thrown
Supported Browser:
P.S: To clear your concept of var, const, and let please go through How to declare variables in different ways in JavaScript?
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