I have an array of timestamps and I want to transform it into dates.
timestamps = [1568666854141, 1568595225048, 1568594645595];
timestamps.forEach(function(d) { d = new Date(d) } )
When I do new Date(d) in debug it gives me Mon Sep 16 2019 16:47:34 GMT-0400 which is good, but if I check my array, it's still the same. It gives me
[1568666854141, 1568595225048, 1568594645595] instead of [Mon Sep 16 2019 16:47:34 GMT-0400, ...]
Why does not every element d reassigns to a date?
forEach can not modify the orgin array, please use map:
let timestamps = [1568666854141, 1568595225048, 1568594645595];
timestamps = timestamps.map(function(d) { return new Date(d) } )
You're creating a new array and creating a new (correct) date value for each element, but not doing anything with the values.
timestamps array) by using map instead of forEach [link to good explanation of the difference]timestamps = timestamps.map(function(d) { return new Date(d) } );
I solved my problem doing this:
timestamps.forEach(function(elem, idx, arr) {arr[idx] = new Date(elem); });
map for this instead (see my answer as well as the other answer); especially if you don't need access to that array for all of the other values.map and forEach otherwise behave very similarly; but this is an important case where you can really benefit from the fact that map returns an array for you. (Check out the link in my answer below for more details on this specifically.)
timestamps.forEach(function(d, i) { timestamps[i] = new Date(d) } )