JS scrapper(s) for webpage(s)

I need some number of javascript-based scraping scripts. - language: must be written in javascript - environment: will run on target webpage in browser (by injection) - target page: pages have some quantity (some more or some less) of elements (around 100-200) with values, values updating by page/site js continuously and periodically elements/sections added/removed. - Task: write JS script that will scrape page and fire callback when changes was: - eat relatively small amount resources (cpu and ram) - fast checking and response - must provide enough good structured unified (must be applicable to other pages) compact js object with scrapped data as output - be coded in good style You can use regular scrapping, parsing DOM, intercepting AJAX calls or any other applicable way that you see (but not do additional server calls). For someone who doing that often it's very easy task. In bid set your expected price for 5 scripts. I need about 5-10 of such pages to be scrapped first time and later probably more.