JavaScript Operators Reference
JavaScript operators are used to assign values, compare values, perform arithmetic operations, and more.
JavaScript Arithmetic Operators
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 » |
| / | 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.
JavaScript Assignment Operators
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.
JavaScript String Operators
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
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.
Conditional (Ternary) Operator
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 » |
Example explained: If the variable "age" is a value below 18, the value of the variable "voteable" will be "Too young", otherwise the value of voteable will be "Old enough".
Logical Operators
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 » |
JavaScript Bitwise Operators
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
The typeof operator returns the type of a variable, object, function or expression:
Example
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
Try it Yourself »
Please observe:
- The data type of NaN is number
- The data type of an array is object
- The data type of a date is object
- The data type of null is object
- The data type of an undefined variable is undefined
You cannot use typeof to define if a JavaScript object is an array (or a date).
The delete Operator
The delete operator deletes a property from an object:
Example
var person = {firstName:"John", lastName:"Doe", age:50, eyeColor:"blue"};
delete person.age; // or delete person["age"];
Try it Yourself »
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.
Note: The delete operator should not be used on predefined JavaScript object properties. It can crash your application.
The in Operator
The in operator returns true if the specified property is in the specified object, otherwise false:
Example
// Arrays
var 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
var 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
Try it Yourself »
The instanceof Operator
The instanceof operator returns true if the specified object is an instance of the specified object:
Example
var cars = ["Saab", "Volvo", "BMW"];
cars instanceof Array; // Returns true
cars instanceof Object; // Returns true
cars instanceof String; // Returns false
cars instanceof Number; // Returns false
Try it Yourself »
The void Operator
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).
Example
<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>
Try it Yourself »
