How to sort javascript Array

Question

I want to sort array by timestamp, but getting unsorted error

var userValue = {
       timestamp,
       username,
       token,
       userid,
       message                      
   };
userArray.push(userValue);

this is the array i am getting

userArray.sort(function(a, b) {
return a[0]['timestamp'] - b[0]['timestamp'];
});

i want sorted array on timestamp basis

Answer 1

This code

userArray[childDatamsg.timestamp] = userValue;

adds an object at timestamp index. This is why you have an array with the length of 1563533788! Instead push the userValue object to the userArray

userArray.push(userValue);

Now, it will have indices from 0.

Then you can sort the array like this:

userArray.sort((a, b) => a.timestamp - b.timestamp)

Answer 2

The following code sorts by the numerical value of timestamps. It ignores skips over array entries and performs string-to-number conversion of timestamps, if necessary. It assumes that besides 'string' and 'number', timstamps are of no other data type.

userArray.filter ( px_item => {
    return (px_item !== undefined);
})
.map ( px_item => {
    if (typeof px_item === "string") {
        return parseInt(px_item);
    } else {
        return px_item;
    }
})
.sort(function(a, b) {
    if (typeof a === "undefined") {
        return -1;
    } else {
        if (typeof b === "undefined") {
            return 1;
        } else {
            return Math.sign ( a['timestamp'] - b['timestamp'] );
        }
    }
});

The original code had the sort function wrong. This function is actually a comparison function to determine the relative order of two elements (which in the given use case would be array entries). The order is expressed as one of the numerical values -1 (a < b), 0 (a = b), and 1 ( a > b ) (in fact, for the result of the comparison to be processed correctly, it suffices that the result has the proper sign, so Math.sign could be eliminated).