JS 操作符整理[推荐收藏]

Arithmetic Operators
算术运算符 Operator Description Example Result
+   Addition
加   x=2
y=2
x+y   4  
-   Subtraction
减   x=5
y=2
x-y   3  
*   Multiplication
乘   x=5
y=4
x*y   20  
/   Division
除   15/5
5/2   3
2.5  
%   Modulus (division remainder)
余数   5%2
10%8
10%2   1
2
0  
++   Increment
递增   x=5
x++   x=6  
--   Decrement
递减   x=5
x--   x=4  
Assignment Operators
赋值运算符 Operator Example Is The 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  
Comparison Operators
比较（关系）运算符 Operator Description Example
==   is equal to
等于   5==8 returns false  
===   is equal to (checks for both value and type)
等于（检查值和类型）*全吻合才算相等   x=5
y="5"

x==y returns true
x===y returns false

 
!=   is not equal
不等于   5!=8 returns true  
>   is greater than
大于   5>8 returns false  
<   is less than
小于   5<8 returns true  
>=   is greater than or equal to
大于等于   5>=8 returns false  
<=   is less than or equal to
小于等于   5<=8 returns true  
Logical Operators
逻辑运算符 Operator Description Example
&&   and
与   x=6
y=3

(x < 10 && y > 1) returns true

 
||   or
或   x=6
y=3

(x==5 || y==5) returns false

 
!   not
非   x=6
y=3

!(x==y) returns true

 
String Operator
串符（连接作用）

A string is most often text, for example "Hello World!". To stick two or more string variables together, use the + operator.
在文字当中使用的比较多，举例来说“Hello World!”要将两个或多个字符串变量衔接在一起的话就得使用 + 符号

txt1="What a very" txt2="nice day!" txt3=txt1+txt2   

The variable txt3 now contains "What a verynice day!".
txt3变量现在包含“What a verynice day!”（把1和2衔接起来了）

To add a space between two string variables, insert a space into the expression, OR in one of the strings.
要给两个字符串变量中间添加空格就得在表达式里插入空格，或在其中的一个加上（空格）

txt1="What a very" txt2="nice day!" txt3=txt1+" "+txt2ortxt1="What a very " txt2="nice day!" txt3=txt1+txt2  

The variable txt3 now contains "What a very nice day!".
现在变量txt3为“What a very nice day!”

Conditional Operator
条件运算符

JavaScript also contains a conditional operator that assigns a value to a variable based on some condition.
JS有根据条件不同给变量不同值的条件运算符

Syntax
语法 variablename=(condition)?value1:value2   
Example
例子 greeting=(visitor=="PRES")?"Dear President ":"Dear "  

If the variable visitor is equal to PRES, then put the string "Dear President " in the variable named greeting. If the variable visitor is not equal to PRES, then put the string "Dear " into the variable named greeting.
如果变量visitor的值等于PRES那么greeting的值就为"Dear President "。如果不为PRES那么greeting的值就为"Dear"

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