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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 |
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 |
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 |
!= | 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 |
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 |
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!”
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
variablename=(condition)?value1:value2 |
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"