JavaScript Operators
JavaScript includes operators same as other languages. An operator performs some operation on single or multiple operands (data value) and produces a result. For example, in 1 + 2, the + sign is an operator and 1 is left side operand and 2 is right side operand. The + operator performs the addition of two numeric values and returns a result.
JavaScript includes following categories of operators.
- Arithmetic Operators
- Comparison Operators
- Logical Operators
- Assignment Operators
- Conditional Operators
- Ternary Operator
Arithmetic Operators
Arithmetic operators are used to perform mathematical operations between numeric operands.
| Operator | Description |
|---|---|
| + | Adds two numeric operands. |
| - | Subtract right operand from left operand |
| * | Multiply two numeric operands. |
| / | Divide left operand by right operand. |
| % | Modulus operator. Returns remainder of two operands. |
| ++ | Increment operator. Increase operand value by one. |
| — | Decrement operator. Decrease value by one. |
The following example demonstrates how arithmetic operators perform different tasks on operands.
Example: Arithmetic Operation
let x = 5, y = 10;
let z = x + y; //performs addition and returns 15
z = y - x; //performs subtraction and returns 5
z = x * y; //performs multiplication and returns 50
z = y / x; //performs division and returns 2
z = x % 2; //returns division remainder 1
The ++ and -- operators are unary operators. It works with either left or right operand only. When used with the left operand, e.g., x++, it will increase the value of x when the program control goes to the next statement. In the same way, when it is used with the right operand, e.g., ++x, it will increase the value of x there only. Therefore, x++ is called post-increment, and ++x is called pre-increment.
Example: Post and Pre Increment/Decrement
let x = 5;
x++; //post-increment, x will be 5 here and 6 in the next line
++x; //pre-increment, x will be 7 here
x--; //post-decrement, x will be 7 here and 6 in the next line
--x; //pre-decrement, x will be 5 here
String Concatenation
The + operator performs concatenation operation when one of the operands is of string type. The following example demonstrates string concatenation even if one of the operands is a string.
Example: + Operator with String
let a = 5, b = "Hello ", c = "World!", d = 10;
a + b; //returns "5Hello "
b + c; //returns "Hello World!"
a + d; //returns 15
b + true; //returns "Hello true"
c - b; //returns NaN; - operator can only used with numbers
Comparison Operators
JavaScript provides comparison operators that compare two operands and return a Boolean value true or false.
| Operators | Description |
|---|---|
| == | Compares the equality of two operands without considering type. |
| === | Compares equality of two operands with type. |
| != | Compares inequality of two operands. |
| > | Returns a Boolean value true if the left-side value is greater than the right-side value; otherwise, returns false. |
| < | Returns a Boolean value true if the left-side value is less than the right-side value; otherwise, returns false. |
| >= | Returns a Boolean value true if the left-side value is greater than or equal to the right-side value; otherwise, returns false. |
| <= | Returns a Boolean value true if the left-side value is less than or equal to the right-side value; otherwise, returns false. |
The following example demonstrates the comparison operators.
Example: JavaScript Comparison Operators
let a = 5, b = 10, c = "5";
let x = a;
a == c; // returns true
a === c; // returns false
a == x; // returns true
a != b; // returns true
a > b; // returns false
a < b; // returns true
a >= b; // returns false
a <= b; // returns true
Logical Operators
In JavaScript, the logical operators are used to combine two or more conditions. JavaScript provides the following logical operators.
| Operator | Description |
|---|---|
| && | && is known as AND operator. It checks whether two operands are non-zero or not (0, false, undefined, null or "" are considered as zero). It returns 1 if they are non-zero; otherwise, returns 0. |
| || | || is known as OR operator. It checks whether any one of the two operands is non-zero or not (0, false, undefined, null or "" is considered as zero). It returns 1 if any one of of them is non-zero; otherwise, returns 0. |
| ! | ! is known as NOT operator. It reverses the Boolean result of the operand (or condition). !false returns true, and !true returns false. |
Example: Logical Operators
let a = 5, b = 10;
(a != b) && (a < b); // returns true
(a > b) || (a == b); // returns false
(a < b) || (a == b); // returns true
!(a < b); // returns false
!(a > b); // returns true
Assignment Operators
JavaScript provides the assignment operators to assign values to variables with less key strokes.
| Assignment operators | Description |
|---|---|
| = | Assigns right operand value to the left operand. |
| += | Sums up left and right operand values and assigns the result to the left operand. |
| -= | Subtract right operand value from the left operand value and assigns the result to the left operand. |
| *= | Multiply left and right operand values and assigns the result to the left operand. |
| /= | Divide left operand value by right operand value and assign the result to the left operand. |
| %= | Get the modulus of left operand divide by right operand and assign resulted modulus to the left operand. |
Example: Assignment operators
let x = 5, y = 10, z = 15;
x = y; //x would be 10
x += 1; //x would be 6
x -= 1; //x would be 4
x *= 5; //x would be 25
x /= 5; //x would be 1
x %= 2; //x would be 1
Ternary Operator
JavaScript provides a special operator called ternary operator :? that assigns a value to a variable based on some condition. This is the short form of the if else condition.
Syntax:
<condition> ? <value1> : <value2>;
The ternary operator starts with conditional expression followed by the ? operator. The second part (after ? and before :) will be executed if the condition turns out to be true. Suppose, the condition returns false, then the third part (after :) will be executed.
Example: Ternary operator
let a = 10, b = 5;
let c = a > b ? a : b; // value of c would be 10
let d = a > b ? b : a; // value of d would be 5
Points to Remember:
- JavaScript includes operators that perform some operation on single or multiple operands (data value) and produce a result.
- JavaScript includes various categories of operators: Arithmetic operators, Comparison operators, Logical operators, Assignment operators, Conditional operators.
- Ternary operator ?: is a short form of if-else condition.