How to check for the presence of an element?

Question

I'm using the .length method in a conditional statement that polls the page for the presence of an externally-loaded object (I can't style it with jQuery until it exists):

 function hackyFunction() { if($('#someObject').length<1) { setTimeout(hackyFunction,50) } else { $('#someObject').someMethod() }} 

Is length the best way to do this?

Answer 1

If you are simply looking for a specific element you can just use document.getElementById

function hackyFunction() {
    if (document.getElementById("someObject")) {
         // Exist
    } else {
         // Doesn't exist
    }
}

Answer 2

Yes you should use .length . You cannot use if ($('#someObject')) ... because the jQuery selectors return a jQuery object, and any object is truthy in JavaScript.

Answer 3

如果你正在寻找一个ID，那么它应该只有一个，所以你也可以这样写：

if($('#someObject')[0])

Answer 4

是的， .length是可以接受的，通常是我使用的。

Answer 5

With jQuery, checking length works fine.

if (!$('#someObject').length) {
    console.log('someObject not present');
}

Of course with vanilla JavaScript, you can just check with document.getElementById (if getting elements by id)

if (document.getElementById('someObject')) {
    console.log('someObject exists');
}