[JaveScript study notes] Those things about operators! (It's all details, I have saved it!)

Operator is also called Operator , A symbol used to realize assignment, comparison and execution of arithmetic operations and other functions

Commonly used operators in JavaScript

• Arithmetic Operator
• Increment and decrement operators
• Comparison operator
• Logical Operators
• Assignment operator

Arithmetic Operator

Operator	description	Instance
+	plus	10+20=30
-	Less	10-20=-10
*	Multiply	10*20=200
/	except	10/20=0.5
%	Take the remainder (modulo)	9%2=1

Floating point precision problem

The highest precision of floating-point numbers is 17 digits, but its precision is far inferior to integers when performing arithmetic calculations.

            var result=0.1+0.2;//0.30000000000000004
            console.log(result);
            console.log(0.07*100);//7.000000000000001

We cannot directly judge whether two floating-point numbers are equal

Increment and decrement operators

If you need to repeatedly add or subtract 1 to a numeric variable, you can use the ++ and – operators to complete.
They can be placed in the front or in the back,
we can bePre-increment operatorwithPost-increment operator

The difference is: add it first or return the value first

            var e=10;
            f=e++ + ++e;
            console.log(f);//22

Comparison operator

It is the operator used when comparing two data. After the comparison operation, a Boolean value will be returned as the result of the comparison operation

Operator name	Description	Case study	result
<	Less than	1<2	true
>	more than the	1>2	false
>=	greater or equal to	2>=2	true
<=	Less than or equal to	3<=2	false
==	Sentence waits, will transform	37==37	true
!=	Unequal	37!=37	false
=== !==	Congruent requirement values ​​and data types are always	37===‘37’	false

Logical Operators

Operator used to perform Boolean operations, and its return value is also a Boolean value

Logical Operators	Description	Case study
&&	versus	true&true
||	or	true||true
！	non-	！true

Short-circuit operation (logical interrupt)

When there are multiple expressions, when the value of the expression next to it can determine the result, the value of the expression on the right is no longer calculated;

            console.log(123||456);//123
            console.log(0||456);//456
            console.log(123||456||789);//123

Take the logical OR as an example. If the
first one is true, then the first value will be returned. If the
first one is false, then the second value will be returned.

Assignment operator

Operators used to assign data to variables

Assignment operator	Description	Case study
=	Direct assignment	var username=‘41’
+= -=	Assign after adding or subtracting a number	var age = 10; age + = 5;
*= /= %=	Assign after multiplying and dividing modulo	var age = 2; age * = 5;

Operator precedence

priority	Operator	order
1	Parentheses	()
2	Unary operator	++ – !
3	Arithmetic Operator	First* /% then +-
4	Relational operator	> >= < <=
5	Equality operator	== != === !==
6	Logical Operators	First && then ||
7	Assignment operator	=
8	Comma operator	，

Exercise

            console.log(4>=6||'peo'!='41'&&!(12*2==144)&&true)//true
            var num=10;
            console.log(5==num/2&&(2+2*num).toString()==='22');//true