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2.4 JS Operators

Example 1: JavaScript Operators part 1

Assign values to variables and add them together:

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 (5 + 2)

The assignment operator (=) assigns a value to a variable.

Example 2: JavaScript Operators part 2 - Assignment

var x = 10;

The addition operator (+) adds numbers:

Example 3: JavaScript Operators part 3 - Adding

var x = 5;
var y = 2;
var z = x + y;

The multiplication operator (*) multiplies numbers.

Example 4: JavaScript Operators part 4 - Multiplying

var x = 5;
var y = 2;
var z = x * y;

JavaScript Arithmetic Operators

Arithmetic operators are used to perform arithmetic on numbers:

Operator	Description
+	Addition
-	Subtraction
*	Multiplication
**	Exponentiation (ES2016)
/	Division
%	Modulus (Division Remainder)
++	Increment
--	Decrement

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
**=	x **= y	x = x ** y

The addition assignment operator (+=) adds a value to a variable.

Example 5: JavaScript Arithmetic part 1 - Assignment

var x = 10;
x += 5;

Assignment operators are fully described in the JS Assignment chapter.

JavaScript String Operators

The + operator can also be used to add (concatenate) strings.

Example 6: JavaScript String Operators

var txt1 = "John";
var txt2 = "Doe";
var txt3 = txt1 + " " + txt2;

The result of txt3 will be:

John Doe

The += assignment operator can also be used to add (concatenate) strings:

Example 7: JavaScript String Operators part 2

var txt1 = "What a very ";
txt1 += "nice day";

The result of txt1 will be:

What a very nice day

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:

Example 8: JavaScript String Operators part 3

var x = 5 + 5;
var y = "5" + 5;
var z = "Hello" + 5;

The result of x, y, and z will be:

10
55
Hello5

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

Comparison operators are fully described in the JS Comparisons chapter.

JavaScript Logical Operators

Operator	Description
&&	logical and
\|\|	logical or
!	logical not

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

Type operators are fully described in the JS Type Conversion chapter.

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	5 & 1	0101 & 0001	0001	1
\|	OR	5 \| 1	0101 \| 0001	0101	5
˜	NOT	~ 5	˜0101	1010	10
^	XOR	5 ^ 1	0101 ^ 0001	0100	4
<<	Zero fill left shift	5 << 1	0101 << 1	1010	10
>>	Signed right shift	5 << 1	0101 << 1	0010	2
>>>	Zero fill right shift	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
Bitwise operators are fully described in the JS Bitwise chapter.

JavaScript Fundamentals course home
Module 2. Variables, Operators and Assignment

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