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Thus you’ll have to verify the month, year and day of a Date separately to detect an invalid date.
Since discovering Moment.js, an open source project, I’ve used it religiously to simplify validation, parsing and manipulation of dates on the client-side.
First, it checks that dates format are valid and then, checks that first date is lower than second date. DEMO What jumps me most about this code is that all you do is in 2 functions.