JSFiddle - React, Tailwind, and code Playground

by lbstr

JavaScript

var datesIn = [
    { date: "12/15/2014", time: 80 },
    { date: "12/29/2014", time: 90 },
    { date: "12/22/2014", time: 10 },
    { date: "12/15/2014", time: 40 },
    { date: "12/22/2014", time: 30 },
    { date: "12/29/2014", time: 10 }
];

var datesOut = (function(dates) {
    if (!dates) { return null; }
    
    var joinedDates = {},
        dateTime, date;
    
    for (var i = 0, l = dates.length; i < l; i++) {
        dateTime = dates[i];
        date = dateTime.date;
        
        if (date) { 
            joinedDates[date] = (joinedDates[date] || 0) + (dateTime.time || 0);
        }
    }
    
    return joinedDates;
})(datesIn);

console.log(datesOut);