JS delayed loading speeds up page opening speed sample code_javascript skills

First, JS lazy loading

The code is as follows:

Copy the code The code is as follows:

Second, JS is loaded last

Insert the following code where JS needs to be inserted:

LOADING...< ;/SPAN>

Of course, that LOADING... you can change it to a small picture you like. It looks very AJAX effective.

Then insert at the bottom of the page:

Copy code The code is as follows:

Yours The JS code is here!
<script>L4EVER.innerHTML=AD_L4EVER.innerHTML;AD_L4EVER.innerHTML="";</script>

Third, JS Finally load

where you want to display ads

where you want to display ads

Copy code The code is as follows:

Judgment Whether the ad position to be displayed exists

Copy the code The code is as follows:

setTimeout usage

The standard syntax of setTimeout is: setTimeout(expression, time (milliseconds)) two parameters.

Here it is important to note the call when the first parameter is a function, assuming it is a function.

1. Function has no parameters:

function alertV(){ alert("000"); }

When the first parameter is not quoted ("" or '') , delay for one second:
setTimeout(alertV,1000);

When the first parameter is added with quotation marks, delay for one second:
setTimeout("alertV()",1000);

2. The function has parameters:

function alertV(event){ alert("keyCode=" event.keyCode); }

At this time it should be set to:
setTimeout(function(){alertV(event);},1000); Otherwise, it will prompt that the parameter is undefined.