Author: Michal Szymanski
Examples:
var x = 5; // assign the value 5 to x
var y = 2; // assign the value 2 to y
var z = x + y; // assign the value 7 to z (x + y)
The assignment operator (=) assigns a value to a
variable.
var x = 10;
The addition operator (+) adds numbers:
var x = 5;
var y = 2;
var z = x + y; // Result 7
The multiplication operator (*) multiplies numbers.
var x = 5;
var y = 2;
var z = x * y; // Result 10
JavaScript Arithmetic Operators
Arithmetic operators are used to perform arithmetic on numbers:
| Operator | Description |
|---|---|
| + | Addition |
| - | Subtraction |
| * | Multiplication |
| ** | Exponentiation (ES6) |
| / | Division |
| % | Modulus (Division Remainder) |
| ++ | Increment |
| -- | Decrement |
Note: Arithmetic operators are fully described in the JS Arithmetic chapter.
JavaScript Assignment Operators
Assignment operators assign values to JavaScript variables.
| Operator | Example | Same As |
|---|---|---|
| = | x = y | x = y |
| += | x += y | x = x + y |
| -= | x -= y | x = x - y |
| *= | x *= y | x = x * y |
| /= | x /= y | x = x / y |
| %= | x %= y | x = x % y |
The addition assignment operator (+=) adds a value to
a variable.
var x = 10;
x += 5; // Result 15
Note: Assignment operators are fully described in the JS Assignment chapter.
JavaScript String Operators
The + operator can also be used to add (concatenate) strings.
var txt1 = "John";
var txt2 = "Doe";
var txt3 = txt1 + " " + txt2; // Result "John Doe"
The += assignment operator can also be used to add (concatenate) strings:
var txt1 = "What a very ";
txt1 += "nice day"; // Result "What a very nice day"
Note: When used on strings, the + operator is called the concatenation operator.
Adding Strings and Numbers
Adding two numbers, will return the sum, but adding a number and a string will return a string:
var x = 5 + 5; // Result 10
var y = "5" + 5; // Result 55
var z = "Hello" + 5; // Result Hello5
Remember: If you add a number and a string, the result will be a string!
JavaScript Comparison Operators
| Operator | Description |
|---|---|
| == | equal to |
| === | equal value and equal type |
| != | not equal |
| !== | not equal value or not equal type |
| > | greater than |
| < | less than |
| >= | greater than or equal to |
| <= | less than or equal to |
| ? | ternary operator |
Note: Comparison operators are fully described in the JS Comparisons chapter.
JavaScript Logical Operators
| Operator | Description |
|---|---|
| && | logical and |
| || | logical or |
| ! | logical not |
Note: Logical operators are fully described in the JS Comparisons chapter.
JavaScript Type Operators
| Operator | Description |
|---|---|
| typeof | Returns the type of a variable |
| instanceof | Returns true if an object is an instance of an object type |
Note: Type operators are fully described in the JS Type Conversion chapter.
Exercises - test your knowledge
Exercise 1
Multiply 10 with 5, and alert the result:
alert(10 *5);
Exercise 2
Divide 10 by 2, and alert the result:
alert(10 / 2);
Exercise 3
x = 10
y = 5
Use the correct assignment operator that will result in x being 15
(same as x = x + y ).
x = 10;
y = 5;
x += y;
Exercise 4
x = 10
y = 5
Use the correct assignment operator that will result in x being 50 (same as x = x * y
).
x = 10;
y = 5;
x *= y;
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