don't mind helping out, i think it's a decent idea.
to clarify your questions where rangana left off:
the double bars are used to re-assign values inline, left - to right, taking the first one that "works".
sometimes called the default operator, double bars can convey multiple possibilities to an assignment (the stuff to the right of an = sign).
picking up mid-function, let's consider an example of a string:
vapp = "hello world"
what val = vapp.value || vapp.innerHTML || window[vapp] || vapp; means is at first glance possibly the same as
val = vapp.value
if it were an input this is the point at which it bails out and the remaining options to the right are never evaluated.
IF vapp.value is "falsy" (which means that the value itself is equal to undefined, false, 0 , NaN, null, etc) then go to the next option to the right; vapp.innerHTML.
remember that strings don't have a .innerHTML so this evaluates to undefined for our example. if it were an element, it would check out here.
continuing, it looks for window[vapp].
if vapp if a string name of a global variable (and that global is not empty) this is where the variable name scenario terminates.
if we made it this far, and we know it was a string, and that it did not meet any of the above conditions, then we must have passed the actual string we wanted to search.
feel free to modify the code and add further possibilities. you could add a .href to grab urls from <A> tags, or substitute "vapp.textContent || vapp.innerText" for "vapp.innerHTML" to grab just the text from an element instead of the HTML. adjust as needed...
now that we have the string to search, we then take the string (vapp or "hello world"), and search it for the sub-string value.
finally, !! turns the truthy-ness of the match operation into an actual boolean, giving us a simple up/down decision about the occurrence of the sub-string.
"||" can replace quite a bit of flow code in some situations.