How to delete a value of an object inside of an array

Question

How come this isn't working? Everything seems right to me. Am I missing something?

Write a function called removePartyKillers that takes in an array like "playlist" (see below) and returns a copy of that playlist where any song longer than 8 minutes has been removed. You can safely assume that a playlist is an array of objects. Each object will have the properties title, artist, and durationInSeconds.

var awesomePlaylist = [
  {
    title: "Hay Day",
    artist: "Robo-Crop",
    durationInSeconds: 378
  }, {
    title: "10,000 Pounds",
    artist: "L-Ton Jonn",
    durationInSeconds: 498,
  }, {
    title: "Caesar's Salad",
    artist: "DJ Dinner Julius",
    durationInSeconds: 600,
  }, {
    title: "The British Are On Their Way",
    artist: "Raul Pevere",
    durationInSeconds: 1095,
  }, {
    title: "13th",
    artist: "The Doctors",
    durationInSeconds: 185,
  }
];

function removePartyKillers(arr) {
    var copy = arr.slice();
    for (var key of copy) {
        for (var key2 in key) {
            if (key2['durationInSeconds'] > (60 * 8)) {
                delete key2;
            }
        }
    }
    return copy;
}

console.log(removePartyKillers(awesomePlaylist));
 /* Results:
  {
    title: "Hay Day",
    artist: "Robo-Crop",
    durationInSeconds: 378
  }, {
    title: "13th",
    artist: "The Doctors",
    durationInSeconds: 185,
  }
]
*/

No because I beleive that's what I did

Ryan Farm
– Ryan Farm

2021-03-05 01:19:54 +00:00
Commented Mar 5, 2021 at 1:19 — Ryan Farm
– Ryan Farm, Commented Mar 5, 2021 at 1:19

Miu · Accepted Answer · 2021-03-05 01:25:16Z

5

I think .filter() is useful in this case.

NOTE: awesomePlaylist itself is NOT an object (associative array) but an array; Therefore You need to manipulate an array. delete manipulates a property in an object.

let awesomePlaylist = [{
  title: "Hay Day",
  artist: "Robo-Crop",
  durationInSeconds: 378
}, {
  title: "10,000 Pounds",
  artist: "L-Ton Jonn",
  durationInSeconds: 498,
}, {
  title: "Caesar's Salad",
  artist: "DJ Dinner Julius",
  durationInSeconds: 600,
}, {
  title: "The British Are On Their Way",
  artist: "Raul Pevere",
  durationInSeconds: 1095,
}, {
  title: "13th",
  artist: "The Doctors",
  durationInSeconds: 185,
}];

function removePartyKillers(arr) {
  return arr.filter(song => song.durationInSeconds <= 8*60)
}

console.log(removePartyKillers(awesomePlaylist));

edited Mar 5, 2021 at 1:25

answered Mar 5, 2021 at 1:22

Miu

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8 Comments

Ryan Farm Over a year ago

Is there a way to do it the way I did it? I'm sure theres just some small error somewhere. I dont want to use any fancy methods haha

Ryan Farm Over a year ago

but the elements inside the array are objects so cant I delete them?

Miu Over a year ago

No, you can't. I've found a mistake in your code. I'm struggling solving it now lol. Just a moment please. Or I hope someone will do it :)

Ryan Farm Over a year ago

I think I understand what you mean then. So, delete would work if I wanted to just delete the durationInSeconds key but still return the remaining 2 keys in that element of the array?

user3909192 Over a year ago

This is the JavaScriptiest solution, but makes a copy. If you didn't need the elements you could splice() them out in a loop. But to put a finer point on it, an Array is an object too, and there are no "associative arrays" in JavaScript, that is a semantic concept foisted on JS Objects by people from other languages. blog.kevinchisholm.com/javascript/…

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Đinh Carabus · Accepted Answer · 2021-03-05 01:32:47Z

delete is for removing object keys only. You cannot remove items of an array with it. Just create a new empty array and add the filtered items (or even better: use .filter):

var awesomePlaylist = [
  {
    title: "Hay Day",
    artist: "Robo-Crop",
    durationInSeconds: 378
  }, {
    title: "10,000 Pounds",
    artist: "L-Ton Jonn",
    durationInSeconds: 498,
  }, {
    title: "Caesar's Salad",
    artist: "DJ Dinner Julius",
    durationInSeconds: 600,
  }, {
    title: "The British Are On Their Way",
    artist: "Raul Pevere",
    durationInSeconds: 1095,
  }, {
    title: "13th",
    artist: "The Doctors",
    durationInSeconds: 185,
  }
];

function removePartyKillers(arr) {
    var copy = [];
    for (var item of arr) {
        if (item['durationInSeconds'] <= (60 * 8)) {
            copy.push(item);
        }
    }
    return copy;
}

console.log(removePartyKillers(awesomePlaylist));

Benjamin Davies · Accepted Answer · 2021-03-05 01:35:35Z

As Miu has already said, delete statements are only used for object properties, not array elements.

The one of the best ways to accomplish this, without using filter, is to loop backwards through the array, removing items if you need to. The reason why you need to go backward is because, if you remove an item, the next item receives its index and you end up skipping it.

var awesomePlaylist = [
  {
    title: "Hay Day",
    artist: "Robo-Crop",
    durationInSeconds: 378
  }, {
    title: "10,000 Pounds",
    artist: "L-Ton Jonn",
    durationInSeconds: 498,
  }, {
    title: "Caesar's Salad",
    artist: "DJ Dinner Julius",
    durationInSeconds: 600,
  }, {
    title: "The British Are On Their Way",
    artist: "Raul Pevere",
    durationInSeconds: 1095,
  }, {
    title: "13th",
    artist: "The Doctors",
    durationInSeconds: 185,
  }
];

function removePartyKillers(arr) {
    var copy = arr.slice();
    for (var i = copy.length - 1; i >= 0; i--) {
        var obj = copy[i];
        if (obj['durationInSeconds'] > (60 * 8)) {
            copy.splice(i, 1);
        }
    }
    return copy;
}

console.log(removePartyKillers(awesomePlaylist));
 /* Results:
  {
    title: "Hay Day",
    artist: "Robo-Crop",
    durationInSeconds: 378
  }, {
    title: "13th",
    artist: "The Doctors",
    durationInSeconds: 185,
  }
]
*/

teddcp · Accepted Answer · 2021-03-05 01:36:42Z

1

The problem is key itself is an object and when it goes to the next line, you are trying to access the 'durationofSeconds' of every possible properties inside the object .You can directly access the intended property with key and check it.

function removePartyKillers(arr) {
    var copy = arr.slice();
    for (var key of copy) {
            if (key['durationInSeconds'] > (60 * 8)) {
                delete key['durationInSeconds'];
            
            //console.log(key)
        }
    }
    return copy;
}

edited Mar 5, 2021 at 1:36

answered Mar 5, 2021 at 1:28

teddcp

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