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JS 操作符整理[推薦收藏]

 更新時間：2011年11月15日 18:49:22   作者：  
JS 操作符主要包括算術(shù)運算符,賦值運算符,比較（關(guān)系）運算符,邏輯運算符,串符（連接作用）,條件運算符等

Arithmetic Operators
算術(shù)運算符

Operator Description Example Result
+ Addition
加		 x=2
y=2
x+y 		4
- Subtraction
減		 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)
余數(shù)		 5%2
10%8
10%2		 1
2
0
++ Increment
遞增		 x=5
x++ 		x=6
-- Decrement
遞減		 x=5
x-- 		x=4

Assignment Operators
賦值運算符

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
比較（關(guān)系）運算符

Operator Description Example
== is equal to
等于		 5==8 returns false
=== is equal to (checks for both value and type)
等于（檢查值和類型）*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
邏輯運算符

Operator Description Example
&& and
與		 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（連接作用）

A string is most often text, for example "Hello World!". To stick two or more string variables together, use the + operator.
在文字當(dāng)中使用的比較多，舉例來說“Hello World!”要將兩個或多個字符串變量銜接在一起的話就得使用 + 符號 

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

txt3=txt1+txt2 

The variable txt3 now contains "What a verynice day!".
txt3變量現(xiàn)在包含“What a verynice day!”（把1和2銜接起來了）

To add a space between two string variables, insert a space into the expression, OR in one of the strings.
要給兩個字符串變量中間添加空格就得在表達式里插入空格，或在其中的一個加上（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!".
現(xiàn)在變量txt3為“What a very nice day!”

Conditional Operator
條件運算符

JavaScript also contains a conditional operator that assigns a value to a variable based on some condition.
JS有根據(jù)條件不同給變量不同值的條件運算符

Syntax
語法

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.
如果變量visitor的值等于PRES那么greeting的值就為"Dear President "。如果不為PRES那么greeting的值就為"Dear"

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