JavaScript comparisons, logical operators, and operators

General comparison and logical operators are used to test true or false .

1. Comparison operators

Comparison operators are used in logical statements to determine whether variables or values are equal.

Assuming x=5, the following table explains the comparison operators:

operator	describe	Compare	return value
==	equal	x==8	false
		x==5	true
===	Absolute equality (both value and type are equal)	x==="5"	false
		x===5	true
!=	not equal to	x!=8	true
!==	Not absolutely equal (one or both of the value and the type are not equal)	x!=="5"	true
		x!==5	false
>	more than the	x>8	false
<	less than	x<8	true
>=	greater or equal to	x>=8	false
<=	less than or equal to	x<=8	true

You can use comparison operators in conditional statements to compare values.

2. Logical operators

Logical operators are used to determine logic between variables or values.

Assuming that x=6 and y=3 are given, the following table explains the logical operators:

operator	describe	example
&&	and	(x < 10 && y > 1) One true
\|\|	or	(x==5 \|\| y==5) is false
!	not	!(x==y) is true

conditional operator

JavaScript also includes conditional operators that assign values to variables based on certain conditions.

grammar

variablename=(condition)?value1:value2

Example:

<!DOCTYPE html>
<html>
<head> 
<meta charset="utf-8"> 
<title></title> 
</head>
<body>

<p>点击按钮检测年龄。</p>
年龄:<input id="age" value="18" />
<p>是否达到投票年龄?</p>
<button onclick="myFunction()">点击按钮</button>
<p id="demo"></p>
<script>
function myFunction()
{
	var age,voteable;
	age=document.getElementById("age").value;
	voteable=(age<18)?"年龄太小":"年龄已达到";
	document.getElementById("demo").innerHTML=voteable;
}
</script>

</body>
</html>

Illustration:

Click the button below to show that the age has reached

3.JS arithmetic operators

Arithmetic operations between AND/OR values.

Assuming y=5, the following table explains these arithmetic operators:

operator	describe	example	x operation result	y operation result
+	addition	x=y+2	7	5
-	Subtraction	x=y-2	3	5
*	multiplication	x=y*2	10	5
/	division	x=y/2	2.5	5
%	Modulo (remainder)	x=y%2	1	5
++	self-increasing	x=++y	6	6
		x=y++	5	6
--	Decrease	x=--y	4	4
		x=y--	5	4

JS assignment operator

The assignment operator is used to assign values to JavaScript variables.

Assuming that x=10 and y=5 are given , the following table explains the assignment operators:

operator	example	Equivalent to	Operation result
=	x=y		x=5
+=	x+=y	x=x+y	x=15
-=	x-=y	x=x-y	x=5
*=	x*=y	x=x*y	x=50
/=	x/=y	x=x/y	x=2
%=	x%=y	x=x%y	x=0

Add strings and numbers

If two numbers are added, the sum of the numbers is returned. If a number is added to a string, a string is returned.

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

The printed result is:

10
55
Hello5

The above content is summarized by me in the novice tutorial. If you don’t understand, you can leave a comment!