A method summary in jQuery that determines whether an object exists

If the jQuery code below is used to determine whether an object exists, it is not available.

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

Because $(" #id ") returns object regardless of the object's existence.

The correct use to determine whether an object exists should be:

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

Use the property length of the jQuery object to determine if > Zero exists.

or

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

Or just use the native Javascript code to determine:

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