Introduction to js comparison and logical operators_Basic knowledge

Comparison and logical operators are used to test true or false.

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

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

运算符	描述	例子
==	等于	x==8 为 false
===	全等（值和类型）	x===5 为 true；x==="5" 为 false
!=	不等于	x!=8 为 true
>	大于	x>8 为 false
<	小于	x<8 为 true
>=	大于或等于	x>=8 为 false
<=	小于或等于	x<=8 为 true

How to use
You can use comparison operators in conditional statements to compare values ​​and then take action based on the results:

if (age<18) document.write("Too young");
You will learn more about conditional statements in the next section of this tutorial.

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

Given x=6 and y=3, the following table explains the logical operators:

运算符	描述	例子
&&	and	(x < 10 && y > 1) 为 true
||	or	(x==5 || y==5) 为 false
!	not	!(x==y) 为 true

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

Syntax
variablename=(condition)?value1:value2
Example
greeting=(visitor=="PRES")?"Dear President ":"Dear ";
If the variable visitor If the value is "PRES", assign the value "Dear President" to the variable greeting, otherwise assign the value "Dear".