How to format timestamps in batch in nodejs

Question

I use koajs to wrote a webapp and I'm having a little trouble with the timestamp format in the database, there are a lot of records and each record is formatted like this.

{
    "_id": {
        "$oid": "61df7c96d649ac83eefa36d3"
    },
    "key": 1286756906,
    "status": 1,
    "name": "bill",
    "starttime": 1642068153784,
    "endtime": 1673604153784
}

I need to show starttime and endtime on the front-end in format like 2022-01-03 10:10:10 .

1. Where should I put the timestamp formatting process on? The front-end or the back-end?

2. My current solution is the back-end, like following

list.js

.get("/list", async (ctx) => {
   let allrecords = await db.myrecords.find();
   await ctx.render("list", {
       allrecords: allrecords.map(d => { d.endtime = new Date(d.endtime).getFullYear() + "-" + (new Date(d.endtime).getMonth()+1 < 10? '0'+ (new Date(d.endtime).getMonth()+1):(new Date(d.endtime).getMonth()+1)) + "-" + new Date(d.endtime).getDate() + " " + new Date(d.endtime).getHours() + ":" + (new Date(d.endtime).getMinutes()< 10  ? '0' + new Date(d.endtime).getMinutes():new Date(d.endtime).getMinutes()); return d}).map(d => { d.starttime = new Date(d.starttime).getFullYear() + "-" + (new Date(d.starttime).getMonth()+1 < 10? '0'+ (new Date(d.starttime).getMonth()+1):(new Date(d.starttime).getMonth()+1)) + "-" + new Date(d.starttime).getDate() + " " + new Date(d.starttime).getHours() + ":" + (new Date(d.starttime).getMinutes()< 10  ? '0' + new Date(d.starttime).getMinutes():new Date(d.starttime).getMinutes()); return d})
   });
})

list.ejs

<% allrecords.forEach(function(item, i){%>
 <div class="item">
 <div>start: <%=item.starttime%></div>
 <div>end: <%=item.endtime%></div>
 </div>
<%})%>

I find this solution too inefficient, is there any other efficient solution?

Thank you.

Answer 1

Doing it on server side is fine, if you only need those time values as strings on client side. For the mapping I would do:

.get("/list", async (ctx) => {
    let allrecords = await db.myrecords.find();
    await ctx.render("list", {
        allrecords: allrecords.map(d => { 
            d.endtime = new Date(d.endtime).toISOString().
                                .replace('T', ' ').substr(0, 19);
            d.starttime = new Date(d.starttime).toISOString().
                                .replace('T', ' ').substr(0, 19);
            return d
        });
    });
})

Then you are creating each of your dates only one single time.