jquery checks if an element exists on the Web page

jquery selectors have a relatively sophisticated processing mechanism, using jquery to get the non-existent elements of the page will not error, it is worth noting that the use of $ (' #tt ') is always the object, even if the page does not have this element. When using jquery to check if an element exists on the page, it cannot be judged in a way that:

if ($(' #tt ')) {//dosomething}

It should be judged based on the length of the element obtained, as follows:

if ($ (' #tt '). Length>0) {//dosomething}

or converted to a DOM object to judge, as follows:

if ($ (' #tt ') [0]) {//dosomething}

jquery checks if an element exists on the Web page