JS operator

Operator

Also known as The operator , Used to implement assignment 、 Symbols for functions such as comparison and arithmetic operations

JS Common operators in

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

Arithmetic operator

Symbols used in arithmetic operations , Used to perform arithmetic operations on two variables or values

Try not to use floating-point numbers to participate in operations , There will be errors  

expression ：

By digital 、 Operator 、 A formula composed of variables

In the end, there will be a result , Back to us , It's called the return value

Increment and decrement operators

Let the numerical variable be added repeatedly 1 Sum minus 1, have access to Increasing （++） and Decline （--） Operator to complete

++ and -- Put it in Before variable , be called Pre increment （ Decline ） Operator , Put it in After variables when , be called Post increment （ Decline ） Operator

Be careful ： The increment decrement operator must be used with variables

++num amount to  num = num + 1

Pre increment operator ：

Add it first , Then return the value

Post increment operator ：

num++ Post increment , It's self imposed 1

Return the original value first , Post autoplus

Summary ：

• When used alone , The running results are the same
• When used in conjunction with other codes , The results will be different
• After ： First the original value operation , Post autoplus
• In front of ： Add it first , Post operation
• Most developers use post , And the code has a single line

Comparison operator

The operator used to compare two data , After comparison , Meeting Returns a Boolean value （true / false） As a result of the comparison operation

== Default conversion data type , It can convert string data type to numeric data type

=== The values and data types on both sides need to be completely consistent

  Logical operators

The operator used to perform Boolean operations , Its return value is also Boolean , Later development is often used to judge multiple conditions

 && On both sides true Will return true, Otherwise return to false

 | | On one side, true return true, On both sides false return false

！ Also known as Inverse character , Used to take a value that is the opposite of a Boolean value

Short-circuit operation （ Logic break ）

The principle of short circuit operation ： When there are multiple expressions （ value ） when , When the value of the expression on the left can determine the result , The value of the expression on the right will no longer be evaluated

Logic and

•   grammar ： expression 1 && expression 2
• If the first expression is true , Then return the expression 2
• If the first expression is false , Then return the expression 1

Logic or

• grammar ： expression 1 && expression 2
• If the first expression is true , Then returns the first expression
• If the first expression is false , Returns the second expression

Assignment operator

Operators used to assign data to variables

  Operator priority

•   In unary operators Logical non priority is high
• Logic and is higher than logic or priority