JS 操作符整理[推荐收藏]_基础知识

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
>=	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

Logical Operators
逻辑运算符

Operator	Description	Example
&&	and 与	x=6 y=3 (x 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+" "+txt2

or

txt1="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"