How jQuery determines whether the object with the specified id exists

How jQuery determines whether the object with the specified id exists: determine whether the length of the object is greater than 0. The code is [if($("selector").length>0){alert('The object exists ');}else{alert('Object does not exist');}].

The operating environment of this tutorial: windows7 system, jquery3.2.1 version, thinkpad t480 computer.

How jQuery determines whether the object with the specified id exists:

jQuery determines whether the object with the specified id exists. You only need to determine whether the length of the object is greater than 0.

Example:

The correct way to judge is as follows:

if($("#object_id").length>0)
{
  alert('对象存在');
}
else
{
  alert('对象不存在');
}

Or directly use the native Javascript code to judge:

if(document.getElementById("id"))
{
alert('对象存在');
}
 else
{
alert('对象不存在');
}

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