javascript - Using moment.js to find the index of an object matching today's date

Question

I am trying to find the index of an object in an array that contains a timestamp that matches the current date. Today is the 27th, so based off of my dataset, it should return the first index. I have tried two solutions, neither of which work for different reasons. I am open to using a solution to either method.

I have tried using an exact string match.

const index = _.findIndex(data, function(day) { 
   return day.timestampUtc === moment().startOf('day').toISOString() })

The above does not work because it is trying to match 2021-01-27T00:00:00Z to 2021-01-27T06:00:00.000Z which never catches because it would return undefined.

I have also tried

const index = _.findIndex(data, function(day) { 
   return moment(day.timestampUtc).day() === moment().day() }) //should return 1, but returns 2

This one didn't work because using moment(day.timestampUtc) would evaluate it to the day before due to timezone offset, so my returned index would be one too high because it evaluates against one day early.

data

[{
  timestampUtc: "2021-01-26T00:00:00Z"
  weatherCodeType: "FLURRIES"
 },
 {
  timestampUtc: "2021-01-27T00:00:00Z"
  weatherCodeType: "RAIN"
 }, //I want this one
{
  timestampUtc: "2021-01-28T00:00:00Z"
  weatherCodeType: "SNOW"
 },
]

question from:https://stackoverflow.com/questions/65926686/using-moment-js-to-find-the-index-of-an-object-matching-todays-date

Answer 1

You should set time to 0 and i think it's better to compare the values, not the strings:

index = _.findIndex(data, (day) => {
  var today = moment().utc()
  today.set({ hour: 0, minute: 0, second: 0, millisecond: 0 })
  return moment.utc(day.timestampUtc).valueOf() === today.valueOf()
})