Question

I am trying to figure out what in the world this jquery selector is doing. When it runs, it is executing on a massive scale and removing it increases execution speed by roughly 95%. The optimized code works fine without it, but I am still trying to figure out what it was doing in the first place.

Here is the original code format:

$("[name='" + this.Name + "']", $(document.body))...

The item I’m trying to figure out is what is after the comma. It’s not a normal part of the selector, as it is outside the main batch of quotes, and I have had no luck at all finding documentation on anything like this. When the code is reduced to

$("[name=\"" + this.Name + "\"]")

then it operates at a massively increased speed (95% faster). Does anyone know what that extra $(document.body) is doing?

Answer 1

The 2nd parameter to the $() function is the context. It’s the same as doing:

$(document.body).find("[name='" + this.Name + "']")

(Which is completely useless as tags aren’t normally outside the body of a document.)

P.S. You don’t need to wrap the 2nd param in $(), it can be a DOM element (or even a selector).

$("[name='" + this.Name + "']", document.body) // this may be faster than
                                               // $(document.body)
$("[name='" + this.Name + "']", 'body')  // This is also valid