JavaScript 判断某年某月有多少天

function  getYearMonthDayNum(year,month){     var   dayNum   =   [31,28,31,30,31,30,31,31,30,31,30,31];     if(new   Date(year,1,29).getDate()==29){         dayNum[1]   =   29;     }     return   dayNum[month-1]; }

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