js根據某天日期計算對應一週日期

前言

記錄一個js方法，用來計算某個日期對應一週的日期，如輸入20190104，頁面結果如下

實現

var searchTime = '20190104';
var mon = "週一 - " + (dealTime(1, searchTime);
var tue = "週二 - " + (dealTime(2, searchTime);
var wed = "週三 - " + (dealTime(3, searchTime);
var thu = "週四 - " + (dealTime(4, searchTime);
var fri = "週五 - " + (dealTime(5, searchTime);
var sat = "週六 - " + (dealTime(6, searchTime);
var sun = "週日 - " + (dealTime(0, searchTime);

//處理時間方法
function dealTime(dayNum, dat) {
    if (dayNum == "0") {
    	dayNum = 7;
    }
    var uom = new Date(), dateStr = '', fday = '';
    fday = dat.substring(6, 8);
    uom.setYear(dat.substring(0, 4));
    uom.setMonth(parseInt(dat.substring(4, 6)) - 1);
    uom.setDate(fday);
 
    if(uom.getDay() == 0){
    	uom.setDate(uom.getDate() - (7 - dayNum));
    }else{
    	uom.setDate(uom.getDate() - (uom.getDay() - dayNum));
    }
    var mon = (uom.getMonth() + 1) + '';
    if (mon.length != 2) {
    	mon = '0' + mon;
    }
    var day = uom.getDate() + '';
    if (day.length != 2) {
    	day = '0' + day;
    }
    dateStr = '' + uom.getFullYear() + mon + day;
    return dateStr;
}