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+" "+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"