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// isValidDate expects the input to be a string of the form MM/DD/YYYY (all ten characters). // // Public domain functions by Darel Rex Finley, 2016. function isValidDate(s) { return s.length==10 && s.charAt(0)>='0' && s.charAt(0)<='9' && s.charAt(1)>='0' && s.charAt(1)<='9' && s.substring(0,2)>='01' && s.substring(0,2)<='12' && s.charAt(2)=='/' && s.charAt(3)>='0' && s.charAt(3)<='9' && s.charAt(4)>='0' && s.charAt(4)<='9' && s.substring(3,5)>='01' && s.substring(3,5)<='31' && s.charAt(5)=='/' && s.charAt(6)>='0' && s.charAt(6)<='9' && s.charAt(7)>='0' && s.charAt(7)<='9' && s.charAt(8)>='0' && s.charAt(8)<='9' && s.charAt(9)>='0' && s.charAt(9)<='9' && s.substring(6)>='1970' && ( s.substring(3,5)!='31' || s.substring(0,2)!='04' && s.substring(0,2)!='06' && s.substring(0,2)!='09' && s.substring(0,2)!='11') && ( s.substring(0,2)!='02' // it's not Feb, or || s.substring(3,5)<='28' // it's Feb but not past the 28th, or || s.substring(3,5)=='29' // it's Feb 29th but && mult4(s.substring(8)) // the year is a multiple of 4 and && (s.substring(8)!='00' // the year is not a multiple of 100.. || mult4(s.substring(6,8)))); } // ..or the year is a multiple of 400 function mult4(twoDigits) { var a=twoDigits.charAt(0), b=twoDigits.charAt(1); if (a=='0' || a=='2' || a=='4' || a=='6' || a=='8') return b=='0' || b=='4' || b=='8'; return b=='2' || b=='6'; } |