A few tips on JS

Source: Internet
Author: User

As the front-end basic work will be used every day JS ... But do we really know about JS, or do we have any tips that we don't know about?

So.. Here are a few tips on JS .....

One: Timer (multiple parameters can be passed)

The first is a general timer, generally we use the Timer 2 parameters, one is a function, one is time.

SetTimeout (function () {  //Functions alert (1);},2000)  //Time

But in fact the timer has a number of parameter parameters, tips:

SetTimeout (num) {  //pass a formal parameter alert (num);},2000,123)//callback parameter
Two: Stitching strings

The problem of stitching strings is often encountered at work, such as when we add content to a BODY element:

Window.onload=function () {document.body.innerhtml= ' <div>div</div><span>span</span></ P>p</p>123 ';}

When these strings are on a single line, this adds no problem, and if we add too much content to this line, this is usually the case:

Window.onload=function () {document.body.innerhtml= ' <div>div</div> ' + ' <span>span</span> ' + ' </p>p</p> ' + ' 123 ';}

This universal approach is duly completed and there is no problem.

Here's a tips that might not be so common:

Window.onload=function () {document.body.innerhtml= ' <div>div</div>\          //After character plus a backslash <span> Span</span></p>p</p>123 ';}

The same, the wood is a bit of a problem!

Three: Console.log ()

Mainly used for printing, debugging information, first, in the Debug console output a Hallo

<script>var a = ' Hallo '; Console.log (a);</script>

OK, no problem, in fact, we can not only output a character, but also output image, style. Now let's add a style to this hallo.

<script>var a = ' Hallo '; Console.log ('%c ' +a, ' font-size:400%;background:blue;color:red; '); </script>

Very reliable ~

Four: tipeof

This is usually used to detect the type of data, which is generally used

var a = [];alert (typeof a)  //Connect with a space, popup object

You can use it.

var a = [];alert (typeof (A))//with () connection, Popup object
V: Nested for loop

First define 2 for loops

for (Var i=0;i<5;i++) {   //i loop for (Var j=0;j<1;j++) {  //j loop if (i==3) {break;  Did not jump out of the I loop, just skipped 3.} alert (i);}}

Sometimes we need to jump out of the big loop so

A:for (var i=0;i<5;i++) {   //give loop a name for (Var j=0;j<1;j++) {if (i==3) {Break A;  Jump out of this loop}alert (i);}}
Six: For Loop

1. Most commonly used

for (Var i=0;i<5;i++) {  //3 value alert (i)}

2. Also commonly used

var i = 0;  Externally defined IFOR (; i<5;i++) {//2 values Alert (i)}

3. Infrequently used

var i = 0;for (;;) {  //0 Values alert (i) if (++i>=5) {//  need to be judged, otherwise dead loop break;}}
Seven: Call
var obj = {  a:function () {alert (this)}}var arr = [1,2,3];obj.a ();  This points to obj

If you want to make this point to arr, just call (arr)

Obj.a.call (arr);

If call () is not pointing, it points to window automatically.

Eight: anonymous function self-executing

Wrong wording

function () {    

Correct notation Plus (parentheses)

(function () {    alert (123);}) ();   Automatically execute alert ();

If you don't want to add parentheses and you want to do it yourself, you can

!function () {alert (123);} ();

Plus operator, also will not error, not only can add!, can also ~, or + (all do not error)

Nine: Creating objects

So so

var arr = new Array (); alert (arr.length);

In fact, can not use the object behind the ();

var arr = new Array;alert (arr.length);

In fact, are a lot of small and small details, write less, do more, how happy a thing ha!

Finally, the details determine success or failure! \ 0.0/

A few tips on JS

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