How to detect a specific page load with javascript?

I have a gallery page with a table that has an id. Each table cell has an img element. How 开发者_运维问答do I test if the current page has a table and those img elements?

I tried:

if ($("#gallery-table img"))
{
alert("Gallery page");
}

but that code runs on every page even if the elements do not exist.

Try

if ($("#gallery-table img").length)
{
   alert("Gallery page");
}

jQuery is returning an object no matter what, so you'll need to see if anything exists in that object.