How to delete data from the javascript object from this data structure?

Question

I need to read all the connection times. (connectionTimes) I need to delete the line - when it will be offline more than online:

    userId: 1,
    connectionTimes:
        [
            {onlineTime:"11:10:30", offlineTime:"11:18:12"}, //delete
            {onlineTime:"11:14:14", offlineTime:"11:52:41"}  //delete
        ]

Delete user id - When times the connection will be empty.

 userId: 1, //delete userid
        connectionTimes:
            [
                //empty connection
            ]

I have this data structure:

var users = [];

    users[0] = {
        userId: 1,
        connectionTimes:
            [
                {onlineTime:"11:10:30", offlineTime:"11:18:12"},
                {onlineTime:"11:14:14", offlineTime:"11:52:41"}
            ]
    }

    users[1] = {
        userId: 2,
        connectionTimes: 
            [
                {onlineTime:"8:08:14", offlineTime:"1:15:00"}
            ]
    }

Andreas Koch · Accepted Answer · 2012-01-23 22:24:12Z

9

You can delete a property from an JavaScript object with the delete operator:

var sampleObject = {
    "key1": "value1",
    "key2": "value"
};
delete sampleObject["key2"];

or like this:

delete sampleObject.key2

See the Mozilla Developer Network JavaScript Reference for more background on the delete operator: https://developer.mozilla.org/en/JavaScript/Reference/Operators/delete

Your specific example would look something like this:

for(var id in users) {
    var user = users[id];
    if (user.connectionTimes.length === 0) {
        delete users[id];
        break
    }

    for(var i=0; i<=user.connectionTimes.length; i++) {
        var connectionTime = user.connectionTimes[i];
        if (connectionTime.onlineTime < connectionTime.offlineTime) {
            delete users[id];
            break;
        }
    }
}

Here is a link to jsFiddle showing the code in action: http://jsfiddle.net/Q86Jd/

edited Jan 23, 2012 at 22:24

answered Jan 23, 2012 at 22:14

Andreas Koch

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2 Comments

Jenan Over a year ago

Here I need - Do not delete the user, but only the lines.

if (connectionTime.onlineTime < connectionTime.offlineTime) {             delete users[id]; //delete only connection time - no user             break;         }

Can you help me?

Jenan Over a year ago

It works:

for (var i = 0; i < user.connectionTimes.length; i++) {             var connectionTime = user.connectionTimes[i];             if (typeof connectionTime != "undefined") {                 if (connectionTime.onlineTime < connectionTime.offlineTime) {                     delete user.connectionTimes[i];                 }              }          }

hugomg · Accepted Answer · 2012-01-23 22:33:25Z

There are many ways to remove things from arrays in Javascript. The mains ones I can think of are

The delete operator. Using it sets the chosen position to undefined and is similar to just setting the element to null. (The main difference is that deleting a key will cause it to be skiped when iterating with the forEach and map array methods).
```
var xs = [0,1,2];
delete xs[1];
console.log(xs); // [0, undefined, 2]
```
The splice method can remove a chunk or the array, moving the remaining elements left to fill it in.
```
var xs = [0,1,2,3];
xs.splice(2, 1); //index, ammount to remove
console.log(xs); // [0,1,3]
```
Setting the array's length property truncates it. This can be used to manually remove elements the old fashioned way when you want more control.
```
var xs = [0,1,2,3];
xs.length = 2;
console.log(xs); // [0,1]
xs.length = 4;
console.log(xs); // [0,1, undefined, undefined]
```

So in your case we might do something like this:

function filter_in_place(array, predicate){
    var j=0;
    for(var i=0; i<arr.length; i++){
        var x = arr[i];
        if(pred(x)){
            arr[j++] = x;
        }
    }
    arr.length = j;
}

for(var i=0; i < users.length; i++){
    filter_in_place( users[i].connections, function(conn){
        /*return if offline larger then online*/
    });
}

filter_in_place(users, function(user){ return user.connections.length > 0; });

Niet the Dark Absol · Accepted Answer · 2012-01-23 22:07:24Z

1

Basically you want to use something like this:

for( var i=0; i<users.length; i++) {
    for( var j=0; j<users[i].connectionTimes.length; j++) {
        if( users[i].connectionTimes[j].onlineTime < users[i].connectionTimes[j].offlineTime) {
            delete users[i].connectionTimes[j];
            j--;
        }
    }
    if( users[i].connectionTimes.length == 0) {
        delete users[i];
        i--;
    }
}

answered Jan 23, 2012 at 22:07

Niet the Dark Absol

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Comments

Jordan Running · Accepted Answer · 2012-01-23 22:23:22Z

This is pretty straightforward. In pseudocode:

declare user, times

for each index in users
  set user  = users[ index ]
  set times = user.connectionTimes

  if times is empty
    then delete users[ index ]

  else
    declare onlineSecs, offlineSecs

    for each index2 in times
      set onlineSecs  = timeInSeconds( times[ index2 ].onlineTime )
      set offlineSecs = timeInSeconds( times[ index2 ].offlineTime )

      if offlineSecs > onlineSecs
        then delete times[ index2 ]

In JavaScript the command to delete a variable is delete and can be used on arrays the same, e.g. delete someArray[ someIdx ];. The implementation of timeInSeconds will be something like this:

function timeInSeconds( timeWithColons ) {
  var hrsMinsSecs = "12:34:56".split(':');

  return ( parseInt( hrsMinsSecs[0] ) * 60 +
           parseInt( hrsMinsSecs[1] )
         ) * 60 +
         parseInt( hrsMinsSecs[2] )
  ;
}

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