Chapter III Basic Concepts (Part III: Operators)

Four. Operators　

Operators include arithmetic, bitwise operator relationship operators, and equality operators. The bitwise operator does not look at the moment.

　　1. Arithmetic operations

Subtraction arithmetic. It's the same as the math book.

% modulo: Essentially, the trigger remainder is taken.

such as: 12%5 result is 2. Can be used to judge odd even numbers.

The "Case 1" table is a gray line of white. The HTML schema is as follows:

    <ulID= "UL1">        <Li></Li>        <Li></Li>        <Li></Li>        <Li></Li>        <Li></Li>        <Li></Li>        <Li></Li>        <Li></Li>        <Li></Li>    </ul>

JS section:

    window.onload=function  () {        var oul=document.getelementbyid (' ul1 ');         var ali=oul.getelementsbytagname (' li ');          for (var i = 0; i < ali.length; i++) {            if(i%2==0) {// take even                ali[i].style.background= ' #f5f5f5 ';}}        ;    }

Even behavior Gray.

"Case two" time conversion rendering

In JS, n seconds =n/60 minutes +n%60 seconds

var n=1989; alert (parseint (n/60) + ' min ' +n%60+ ' s ')

Output to

　　2. Increment and decrement operators

var age=29;

++age;

Equivalent to age=age+1. The predecessor decrement (--age) is similar to this. The predecessor Operation Mr. Foo calculates the second sentence, and then brings it into the first sentence. The post operator instead.

　　3. Relationship Comparison

(1) <, >, <=, >= and mathematical definitions are exactly the same. The result of the operation returns a Boolean value.

(2) Equality (= =) will typically convert two data to a similar data type before comparing (implicit conversion), such as 55== "55". Again, for example, Null==undefined returns the true,null===undefined return is false, because the data types are different.

(3) = = = Congruent: more stringent equivalence. 55! = = = "55"

! = Implicit conversion type after comparison

!== Direct comparison without conversion

Note: = is an assignment operator, not a comparer.

　　4. Boolean operators

Logical NON (!)

Take the inverse, contact the Boolean () function, the following judgments are established.

Object	False
Empty string	True
String	False
0	True
Number	False
Null	True
NaN	True
Undefined	True

&&: Must be set up at the same time. Is true.

|| Or: Multiple conditions one of the conditions is true.

! No: Take the reverse. The alert (!true) result is false.

parentheses represent precedence operations.

　　5. Assignment operators

is actually a shorthand for various assignments. The main purpose is to simplify assignment operations, and use them without any performance gains.

= Simple assignment.

+=:i+=2 means i=i+2.

The above two are used more.

-=:i-=2 means i=i-2.

*=,/=, and%= are similar.

　　6. Comma

A comma is a separator that is used to complete multiple operations on a single line.

Chapter III Basic Concepts (Part III: Operators)