Selecting the src of an input using ID in JQuery

If I understand correctly, what you are looking for is whether or not a given element with the id #src-img has an attribute src assigned. For this you can use different selectors.

Example to clarify:

['#src-imgA', '#src-imgB', '#src-imgC'].forEach(function(id) {
    console.log(id);
    console.log(!!$(id).attr('src'));
    console.log(!!$(id + "[src]").length);
    console.log('-------');
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script><imgid="src-imgA" />
<img id="src-imgB" src="" />
<img id="src-imgC" src="/o/meu/url" />

The commented result:

#src-imgA
false     // o elemento existe, mas o atributo "src" está vazio/não existe
false     // o elemento existe mas como não tem atributo "src" o seletor falha
-------
#src-imgB
false     // o elemento existe mas o atributo "src" está vazio
true      // o elemento existe e tem um atributo "src" (ele não verifica se está vazio)
-------
#src-imgC
true
true
-------

You could use .attr like this:

if($('#img').attr('src') != ""){

}

In this way it will check if the src attribute of its image element is not empty and if not, if it is true, otherwise it can put an else.

When jQuery does not find any element, it comes with an empty% object. This is not considered logically false by javascript, so the code you posted is equivalent to:

if (true) {
}

What you can do is take a look at the arraylike property of the jQuery return. If you did not get any element, length would be zero. Then you can compare ...

if ($("blablabla").length !== 0) {
}

Or use direct length, since zero is considered logically false.

if ($("blablabla").length) {
}