added examples/js/looping-over-all-symbols-of-specific-exchanges.js and examples/js/looping-over-specific-symbols-of-all-exchanges.js fix #4181 [ci skip]
added examples/js/looping-over-all-symbols-of-specific-exchanges.js and examples/js/looping-over-specific-symbols-of-all-exchanges.js fix #4181 [ci skip]