JSFiddle - React, Tailwind, and code Playground

JavaScript

var total = [[1370923200000, "66"],[1371009600000, "42"],[1371096000000, "23"]];
    var successful = [[1370923200000, "5"],[1371096000000, "2"],[1371182400000, "0"]];
    var combined = {};

    for(var i=0; i<total.length; i++){
        combined[total[i][0]] = {date: total[i][0], total: total[i][1]};
    }

    for(var i=0; i<successful.length; i++){
        if(successful[i][0] in combined){
            combined[successful[i][0]].successful = successful[i][1];
        }
        else{
            combined[successful[i][0]] = {
                date: successful[i][0], successful: successful[i][1]
            };
        }
    }

    var result = [];
    for(var key in combined){
        result.push(combined[key]);
    }
    alert(result.toSource());