How to sort objects from js array, by object key/value

Question

I have an array which contains many objects. I am trying to sort the array based on the key value of each object.

So, the object looks like this:

var info = [ 
    {name: 'Adam', age: '1987-01-09T18:23:20.000Z'}, 
    {name: 'Issac', age: '1988-09-02T11:17:11.000Z'}, 
    {name: 'Tom', age: '2003-08-07T13:07:03.000Z'}, 
    {name: 'Jane', age: '1997-17-01T14:57:41.000Z'} 
]; 

I am trying saved the new (sorted) data into a variable called sorted ;

 var sorted = info.forEach(function(person) {
    var age = moment(String(person.age)).format('MM/DD/YYYY'); 

    return age 

    }, this);


 console.log(sorted)

So, I have momentjs, to change the date into a time format that can easily be sorted, but the sorted console.log shows me undefined .

Honestly, I don't even know how sorting functions work. At least it should return the age from the loop and thus console.log() should not have been empty

Answer 1

forEach isn't used to sort, neither is it used to change an array. For sorting, you should use sort .

The sort function sorts an array by comparing elements in pairs. You need to give it a function that will "compare" two elements. The "compare" function takes in two argument a and b , and should return a negative number if a<b , 0 if they are the same, and a positive number if a>b .

Therefore, the code below could works:

var info = [ 
    {name: 'Adam', age: '1987-01-09T18:23:20.000Z'}, 
    {name: 'Issac', age: '1988-09-02T11:17:11.000Z'}, 
    {name: 'Tom', age: '2003-08-07T13:07:03.000Z'}, 
    {name: 'Jane', age: '1997-12-01T14:57:41.000Z'} 
];

info.sort(function (a, b) {
    return (new Date(a.age)).getTime() - (new Date(b.age)).getTime()
})

Also notice that the fourth date you have given - 1997-17-01T14:57:41.000Z , is invalid since month number must be less than 13.

Answer 2

Try for this:

var arrayOfObject = [ 
    {name: 'Adam', age: '1987-01-09T18:23:20.000Z'}, 
    {name: 'Issac', age: '1988-09-02T11:17:11.000Z'}, 
    {name: 'Tom', age: '2003-08-07T13:07:03.000Z'}, 
    {name: 'Jane', age: '1997-12-01T14:57:41.000Z'} 
];

arrayOfObject.sort(function (a, b) {
    return ((new Date(a.age)).getTime() - (new Date(b.age)).getTime());
})