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JavaScript operators are used to assign values, compare values, perform arithmetic operations, and more
Arithmetic operators are used to perform arithmetic between variables and/or values.
Given that y = 5, the table below explains the arithmetic operators:
Operator | Description | Example | Result in y | Result in x | Try it |
---|---|---|---|---|---|
+ | Addition | x = y + 2 | y = 5 | x = 7 | Try it » |
- | Subtraction | x = y - 2 | y = 5 | x = 3 | Try it » |
* | Multiplication | x = y * 2 | y = 5 | x = 10 | Try it » |
* | Exponentiation (ES2016) | x = y ** 2 | y = 5 | x = 25 | Try it » |
/ | Division | x = y / 2 | y = 5 | x = 2.5 | Try it » |
% | Modulus (division remainder) | x = y % 2 | y = 5 | x = 1 | Try it » |
++ | Increment | x = ++y | y = 6 | x = 6 | Try it » |
x = y++ | y = 6 | x = 5 | Try it » | ||
-- | Decrement | x = --y | y = 4 | x = 4 | Try it » |
x = y-- | y = 4 | x = 5 | Try it » |
For a tutorial about arithmetic operators, read our JavaScript Arithmetic Tutorial.
Assignment operators are used to assign values to JavaScript variables.
Given that x = 10 and y = 5, the table below explains the assignment operators:
Operator | Example | Same As | Result in x | Try it |
---|---|---|---|---|
= | x = y | x = y | x = 5 | Try it » |
+= | x += y | x = x + y | x = 15 | Try it » |
-= | x -= y | x = x - y | x = 5 | Try it » |
*= | x *= y | x = x * y | x = 50 | Try it » |
/= | x /= y | x = x / y | x = 2 | Try it » |
%= | x %= y | x = x % y | x = 0 | Try it » |
For a tutorial about assignment operators, read our JavaScript Assignment Tutorial.
The + operator, and the += operator can also be used to concatenate (add) strings.
Given that text1 = "Good ", text2 = "Morning", and text3 = "", the table below explains the operators:
Operator | Example | text1 | text2 | text3 | Try it |
---|---|---|---|---|---|
+ | text3 = text1 + text2 | "Good " | "Morning" | "Good Morning" | Try it » |
+= | text1 += text2 | "Good Morning" | "Morning" | "" | Try it » |
Comparison operators are used in logical statements to determine equality or difference between variables or values.
Given that x = 5, the table below explains the comparison operators:
Operator | Description | Comparing | Returns | Try it |
---|---|---|---|---|
== | equal to | x == 8 | false | Try it » |
x == 5 | true | Try it » | ||
=== | equal value and equal type | x === "5" | false | Try it » |
x === 5 | true | Try it » | ||
!= | not equal | x != 8 | true | Try it » |
!== | not equal value or not equal type | x !== "5" | true | Try it » |
x !== 5 | false | Try it » | ||
> | greater than | x > 8 | false | Try it » |
< | less than | x < 8 | true | Try it » |
>= | greater than or equal to | x >= 8 | false | Try it » |
<= | less than or equal to | x <= 8 | true | Try it » |
For a tutorial about comparison operators, read our JavaScript Comparisons Tutorial.
The conditional operator assigns a value to a variable based on a condition.
Syntax | Example | Try it |
---|---|---|
variablename = (condition) ? value1:value2 | voteable = (age < 18) ? "Too young":"Old enough"; | Try it » |
Logical operators are used to determine the logic between variables or values.
Given that x = 6 and y = 3, the table below explains the logical operators:
Operator | Description | Example | Try it |
---|---|---|---|
&& | and | (x < 10 && y > 1) is true | Try it » |
|| | or | (x === 5 || y === 5) is false | Try it » |
! | not | !(x === y) is true | Try it » |
Bit operators work on 32 bits numbers. Any numeric operand in the operation is converted into a 32 bit number. The result is converted back to a JavaScript number.
Operator | Description | Example | Same as | Result | Decimal |
---|---|---|---|---|---|
& | AND | x = 5 & 1 | 0101 & 0001 | 0001 | 1 |
| | OR | x = 5 | 1 | 0101 | 0001 | 0101 | 5 |
~ | NOT | x = ~ 5 | ~0101 | 1010 | 10 |
^ | XOR | x = 5 ^ 1 | 0101 ^ 0001 | 0100 | 4 |
<< | Left shift | x = 5 << 1 | 0101 << 1 | 1010 | 10 |
>> | Right shift | x = 5 >> 1 | 0101 >> 1 | 0010 | 2 |
The examples above uses 4 bits unsigned examples. But JavaScript uses 32-bit signed numbers.
Because of this, in JavaScript, ~ 5 will not return 10. It will return -6.
~00000000000000000000000000000101 will return 11111111111111111111111111111010
The typeof operator returns the type of a variable, object, function or expression:
typeof "John"
// Returns string
typeof 3.14
// Returns number
typeof NaN
// Returns number
typeof false
// Returns boolean
typeof [1, 2, 3, 4] // Returns object
typeof {name:'John', age:34}
// Returns object
typeof new Date()
// Returns object
typeof function () {} // Returns function
typeof myCar
// Returns undefined (if myCar is not declared)
typeof null
// Returns object
Please observe:
You cannot use typeof to define if a JavaScript object is an array (or a date).
The delete operator deletes a property from an object:
const person = {
firstName:"John",
lastName:"Doe",
age:50,
eyeColor:"blue"
};
delete person.age; // or delete person["age"];
The delete operator deletes both the value of the property and the property itself.
After deletion, the property cannot be used before it is added back again.
The delete operator is designed to be used on object properties. It has no effect on variables or functions.
The in operator returns true if the specified property is in the specified object, otherwise false:
// Arrays
const cars = ["Saab", "Volvo", "BMW"];
"Saab" in cars // Returns false (specify the index number instead of value)
0 in cars // Returns true
1 in cars // Returns true
4 in cars // Returns false (does not exist)
"length" in cars // Returns true (length is an Array property)
// Objects
const person = {firstName:"John", lastName:"Doe", age:50};
"firstName" in person // Returns true
"age" in person // Returns true
// Predefined objects
"PI" in Math // Returns true
"NaN" in Number // Returns true
"length" in String // Returns true
The instanceof operator returns true if the specified object is an instance of the specified object:
const cars = ["Saab", "Volvo", "BMW"];
(cars instanceof Array) // Returns true
(cars instanceof Object) // Returns true
(cars instanceof String) // Returns false
(cars instanceof Number) // Returns false
The void operator evaluates an expression and returns undefined. This operator is often used to obtain the undefined primitive value, using "void(0)" (useful when evaluating an expression without using the return value).
<a href="javascript:void(0);">
Useless link
</a>
<a href="javascript:void(document.body.style.backgroundColor='red');">
Click me to change the background color of body to red
</a>