An example tutorial on determining whether an object exists in jQuery

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.

Correct useTo determine whether the object existsYou should use:

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

Use the jQuery object's property length to determine if > 0 it exists.

or

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

Or directly use the native Javascript code to judge:

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

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