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
xy
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+" "+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"