JavaScript Programming Learning Skills Summary _javascript Skills

This example for you to share the JavaScript programming learning skills for your reference, the specific contents are as follows

1. Variable Conversion

Varmyvar= "3.14159",

str= "" +myvar,//tostring

int=~~myvar,//tointeger

float=1*myvar,//tofloat

bool=!! Myvar,/*toboolean-anystringwithlength

andanynumberexcept0aretrue*/

Array=[myvar];//toarray

However, the conversion date (new Date (MyVar)) and the regular expression (new RegExp (MyVar)) must use a constructor to use a simplified form such as/pattern/flags when creating regular expressions.

2, take the whole to convert to the numerical type at the same time

When a character variable participates in an operation, JS automatically converts it to a numeric type (if it cannot be converted to Nan)

' 10.567890 ' |

//Result:

All numeric values in//js are double-precision floating-point numbers, so In the bitwise operation, JS will first convert these digital arithmetic to integers, and then perform the operation

//| is binary or, x|0 is always equal to x;^ or, same 0 1, so x^0 is always equal to X, as to ~ is to take the reverse, two times after the value of course is the same

10.567890 ' ^0

/Result: ten

-2.23456789|0

//Results:-2

3, Date conversion value

JS itself the internal representation of time is the Unix timestamp, in milliseconds the current distance from January 1, 1970 0 O'Clock time Unit

vard=+newdate ();//1295698416792

4, class array object to the array

Vararr=[].slice.call (arguments) The

following example uses the more absolute

functiontest () {

varres=[' item1 ', ' item2 ']

res= Res.concat (Array.prototype.slice.call (arguments))//Method 1

Array.prototype.push.apply (res,arguments)//Method 2

}

5, the conversion between the system

(int). ToString (;//convertsinttohex,eg12=>) "C"

(int). ToString (8);//convertsinttooctal,eg.12=> "14"

parseint (string,16)//convertshextoint,eg. " FF "=>255

parseint (string,8)//convertsoctaltoint,eg." =>16

inserts an array into the location specified by another array

vara=[1,2,3,7,8,9];

varb=[4,5,6];

varinsertindex=3;

A.splice.apply (A,array.prototype.concat (insertindex,0,b));

6. Delete array elements

vara=[1,2,3,4,5];

A.splice (3,1);//a=[1,2,3,5]

You may wonder why you should use splice instead of Delete, because using delete will leave a void in the array, and the subscript below is not decremented.
7, to determine whether IE

varie=/* @cc_on!@*/false;

Such a simple words can be judged whether ie, too ...

In fact, there are more wonderful ways, please see the following

Edithttp://www.lai18.com

//Seemingly is the shortest, the use of IE does not support the standard ECMAScript in the array of the last comma ignored mechanism

varie=!-[1,];

Using the condition annotation of IE,

varie=/* @cc_on!@*/false;

or the conditional annotation

varie//@cc_on =1;

IE does not support vertical tab

varie= ' V ' = = ' V ';

Principle ditto
varie=!+ "v1";

To learn this moment feel oneself weak burst.

Try to make use of the native method

To find the maximum number in a set of numbers, we might write a loop, for example:

VARNUMBERS=[3,342,23,22,124];

varmax=0;

For (Vari=0;i

if (numbers[i]>max) {

max=numbers[i];

}

}

Alert (max);

In fact, using the native method can be more simple to achieve

VARNUMBERS=[3,342,23,22,124];

Numbers.sort (function (a,b) {returnb-a});

Alert (numbers[0]);

Of course, the most concise way is:

Math.max (12,123,3,2,433,4);//returns433

You can do this now.

[Xhtml]view plaincopy

Math.max.apply (math,[12,123,3,2,433,4])//MAX

Math.min.apply (math,[ 12,123,3,2,433,4])//Take the minimum value

8. Generate Random Number

Math.random (). toString (). substring (2);//tostring () The parameter of the function is base and the range is 2~36.

math.random (). toString. substring (2);

Exchange two variable values without a third party variable

A=[B,B=A][0];

9. Event Delegation

The JS code is as follows:

Classiceventhandlingexample

(function () {

Varresources=document.getelementbyid (' resources ');

Varlinks=resources.getelementsbytagname (' a ');

Varall=links.length;

For (vari=0;i

//attachalistenertoeachlink

links[i].addeventlistener (' click ', Handler,false);

};

Functionhandler (e) {

varx=e.target;//getthelinkthatwasclicked

alert (x);

E.preventdefault ();

};

}) ();

Use event Delegation to write more elegant:

(function () {

Varresources=document.getelementbyid (' resources ');

Resources.addeventlistener (' click ', Handler,false);

Functionhandler (e) {

Varx=e.target;//getthelinktha

if (x.nodename.tolowercase () = = ' A ') {

alert (' Eventdelegation: ' +x);

E.preventdefault ();

}

;

}) ();

10, the detection of IE version

Var_ie= (function () {

varv=3,div=document.createelement (' div '), all=div.getelementsbytagname (' I ');

while (

div.innerhtml= ',

all[0]

);

returnv>4?v:false;

} ());

JavaScript version detection

Do you know which version of JavaScript your browser supports?

Varjs_ver=[];

(Number.prototype.toFixed)? Js_ver.push ("1.5"): false;

([].indexof&&[].foreach)? Js_ver.push ("1.6"): false;

((function () {try{[a,b]=[0,1];returntrue;} catch (ex) {Returnfalse;}}) ())? Js_ver.push ("1.7"): false;

([].reduce&&[].reduceright&&json)? Js_ver.push ("1.8"): false;

("". Trimleft)? Js_ver.push ("1.8.1"): false;

Js_ver.supports=function ()

{

if (Arguments[0]) return

(!!) ~this.join (). IndexOf (arguments[0]+ ",") + ",");

else return

(this[this.length-1]);

Alert ("Latestjavascriptversionsupported:" +js_ver.supports ());

Alert ("Supportforversion1.7:" +js_ver.supports ("1.7"));

11, determine whether the property exists

bad:thiswillcauseanerrorincodewhenfooisundefined

if (foo) {

dosomething ();

}
Good:thisdoesn ' Tcauseanyerrors. However,evenwhen

//fooissettonullorfalse,theconditionvalidatesastrue

if (typeoffoo!= "undefined") {

DoSomething ();

}
BETTER:THISDOESN ' tcauseanyerrorsandinaddition

//valuesnullorfalsewon ' tvalidateastrue

if (window.foo ) {

dosomething ();

}

In some cases, we have deeper structures and need more appropriate checks when

Ugly:wehavetoproofexistenceofevery

//objectbeforewecanbesurepropertyactuallyexists

if (window.oFoo &&ofoo.obar&&ofoo.obar.baz) {

dosomething ();

}

In fact, the best way to detect whether a property exists is:

if ("opera" Inwindow) {

console.log ("opera");

} else{

console.log ("Notopera");

}

12, detect whether the object is an array

Varobj=[];

Object.prototype.toString.call (obj) = = "[Objectarray]";

The above is the entire content of this article, I hope to learn JavaScript program to help you.