Code to determine whether Id exists under Jquery_jquery

1. Determine whether the object exists

If the following jQuery code is used to determine whether an object exists, it cannot be used

if($("#id") ){
}else{}

Because $("#id") will return object regardless of whether the object exists.

To correctly determine whether an object exists, you should use:

if($("#id").length>0){}else{}

Use jQuery object Use the length attribute to determine if > 0, it exists.

or
if($("#id")[0]){} else {}

or directly use native Javascript code to judge:

if(document.getElementById("id")){} else {}

2. Find child nodes according to the parent node

jQuery's children() returns the matching object The byte point
children() returns the child point of the matching object

one

jQuery code and functions:
function jq(){
alert($(“#ch”).children().html());
}
$(“#ch” ).children() gets the object [ two ]. So the result of .html() is "two"

3. Find the parent node according to the child node




jQuery code and functions
Jquery .ready ({
alert($(“#ch”).children(“#sp”).html());
});
$(“#ch”).children() Get the object [twothree ].
$(“#ch”).children(“#sp”) filter to get [three ]