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JavaScript Operators

In this tutorial you will learn how to manipulate or perform the operations on variables and values using the operators in JavaScript.

What are Operators in JavaScript

Operators are symbols or keywords that tell the JavaScript engine to perform some sort of actions. For example, the addition (+) symbol is an operator that tells JavaScript engine to add two variables or values, while the equal-to (==), greater-than (>) or less-than (<) symbols are the operators that tells JavaScript engine to compare two variables or values, and so on.

The following sections describe the different operators used in JavaScript.

JavaScript Arithmetic Operators

The arithmetic operators are used to perform common arithmetical operations, such as addition, subtraction, multiplication etc. Here's a complete list of JavaScript's arithmetic operators:

Operator Description Example Result
+ Addition $x + $y Sum of $x and $y
- Subtraction $x - $y Difference of $x and $y.
* Multiplication $x * $y Product of $x and $y.
/ Division $x / $y Quotient of $x and $y
% Modulus $x % $y Remainder of $x divided by $y

The following example will show you these arithmetic operators in action:

var x = 10;
var y = 4;
alert(x + y); // 0utputs: 14
alert(x - y); // 0utputs: 6
alert(x * y); // 0utputs: 40
alert(x / y); // 0utputs: 2.5
alert(x % y); // 0utputs: 2

JavaScript Assignment Operators

The assignment operators are used to assign values to variables.

Operator Description Example Is The Same As
= Assign x = y x = y
+= Add and assign x += $ x = x + y
-= Subtract and assign x -= y x = x - y
*= Multiply and assign x *= y x = x * y
/= Divide and assign quotient x /= y x = x / y
%= Divide and assign modulus x %= y x = x % y

The following example will show you these assignment operators in action:

var x;    // Declaring Variable
 
x = 10;
alert(x); // Outputs: 10
 
x = 20;
x += 30;
alert(x); // Outputs: 50
 
x = 50;
x -= 20;
alert(x); // Outputs: 30
 
x = 5;
x *= 25;
alert(x); // Outputs: 125
 
x = 50;
x /= 10;
alert(x); // Outputs: 5
 
x = 100;
x %= 15;
alert(x); // Outputs: 10

JavaScript String Operators

There are two operators which can also used be for strings.

Operator Description Example Result
+ Concatenation str1 + str2 Concatenation of str1 and str2
+= Concatenation assignment str1 += str2 Appends the str2 to the str1

The following example will show you these string operators in action:

var str1 = "Hello";
var str2 = " World!";
 
alert(str1 + str2); // Outputs: Hello World!
 
str1 += str2;
alert(str1); // Outputs: Hello World!

JavaScript Incrementing and Decrementing Operators

The increment/decrement operators are used to increment/decrement a variable's value.

Operator Name Effect
++x Pre-increment Increments x by one, then returns x
x++ Post-increment Returns x, then increments x by one
--x Pre-decrement Decrements x by one, then returns x
x-- Post-decrement Returns x, then decrements x by one

The following example will show you how increment and decrement operators actually work:

var x; // Declaring Variable
 
x = 10;
alert(++x); // Outputs: 11
alert(x);   // Outputs: 11
 
x = 10;
alert(x++); // Outputs: 10
alert(x);   // Outputs: 11
 
x = 10;
alert(--x); // Outputs: 9
alert(x);   // Outputs: 9
 
x = 10;
alert(x--); // Outputs: 10
alert(x);   // Outputs: 9

JavaScript Logical Operators

The logical operators are typically used to combine conditional statements.

Operator Name Example Result
&& And x && y True if both x and y are true
|| Or x || y True if either x or y is true
! Not !x True if x is not true

The following example will show you how these logical operators actually work:

var year = 2018;
 
// Leap years are divisible by 400 or by 4 but not 100
if((year % 400 == 0) || ((year % 100 != 0) && (year % 4 == 0))){
    alert(year + " is a leap year.");
} else{
    alert(year + " is not a leap year.");
}

You will learn about conditional statements in JavaScript if/else chapter.


JavaScript Comparison Operators

The comparison operators are used to compare two values in a Boolean fashion.

Operator Name Example Result
== Equal x == y True if x is equal to y
=== Identical x === y True if x is equal to y, and they are of the same type
!= Not equal x != y True if x is not equal to y
!== Not identical x !== y True if x is not equal to y, or they are not of the same type
< Less than x < y True if x is less than y
> Greater than x > y True if x is greater than y
>= Greater than or equal to x >= y True if x is greater than or equal to y
<= Less than or equal to x <= y True if x is less than or equal to y

The following example will show you these comparison operators in action:

var x = 25;
var y = 35;
var z = "25";
 
alert(x == z);  // Outputs: true
alert(x === z); // Outputs: false
alert(x != y);  // Outputs: true
alert(x !== z); // Outputs: true
alert(x < y);   // Outputs: true
alert(x > y);   // Outputs: false
alert(x <= y);  // Outputs: true
alert(x >= y);  // Outputs: false

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