Notes on the use of setInterval and setTimeout in jQuery_jquery

When writing timers in the past, I always used to directly

setInterval("fn()",2000);
Recently I encountered a problem. When writing timers using jquery, fn always appeared. Non-existent error message, as follows

$(function(){setInterval("fn()",2000);})
The solution is to remove the quotes and brackets and use the most original method

$(function(){setInterval(fn,2000);})
The other way is to write an extension of jq, as follows

Copy the code The code is as follows:

$(function(){
$.extend({
fn:function(){
alert(" im fn!");
}
});
setInterval("$.fn()",2000);
});

All of the above are written There is no problem. But what if you need to pass parameters?

Like the first way of writing above,

$(function(){setInterval(fn,2000);})
If written as

$(function() {setInterval(fn(para),2000);})
reported an error. This one is more classic and more idiotic.

At this time you can build in a function and write it as

$(function(){setInterval(function(){fn(para)},2000);})
This is also possible of.

As for how to deliver the second method, this is simpler, so I won’t say more.

Post it to the blog for memory use only, it’s all basic! This is also where beginners tend to make mistakes!


//==========================

Let me add the second type of parameter passing. method.

Look at the code first

Copy the code The code is as follows:

$( function(){
$start = 1;
$.extend({
a:function(t){
$index = t;
alert($index);
$start ;
}
});
setInterval("$.a(" $start ")",2000);
});

Some People would try to write like this, and what would be the result? The result is the alert, which is always 1 and will not increase. What needs to be noted here is the first parameter in setInterval. This is a statement, enclosed in double quotes, and the content inside will be interpreted as a variable. If you follow the above writing method, it is equivalent to

setInterval("$.a(1)",2000);
Then the result is understandable. The correct way to write it is of course

Copy the code The code is as follows:

$(function() {
$start = 1;
$.extend({
a:function(t){
$index = t;
alert($index);
$start;
}
});
setInterval("$.a($start)",2000);
});

At this time $start will be interpreted as variables. The statement is equivalent to function(){a(variable)}, not function(){a(value)}.