Filtering An Array (JS)

Question

I am having trouble filtering through this array that contains objects. An explanation would be greatly appreciated.

Instructions:

// Using filter(), return only your friends of the array of people below. //Assign it to a variable called 'trueFriends'.

My Solution:

var trueFriends = [];

peopleIknow.filter(function(){
  for(var i = 0; i < peopleIknow.length; i++){
    if (peopleIknow[i].friend == true){
      trueFriends.push(peopleIknow[i]);
    }
  }
});

var peopleIknow = [
  { name: "Steve", friend: true },
  { name: "Dan", friend: false },
  { name: "Bart", friend: true },
  { name: "Sarah", friend: false },
  { name: "Michelle", friend: false },
  { name: "Holly", friend: true }
];

The issue with filter is that it expects the callback to be called for each item in the array. developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/… has a more in depth explanation. — Travis J
– Travis J, Commented May 4, 2018 at 22:08

Muhammad Usman · Accepted Answer · 2018-05-04 22:09:49Z

2

You should not use for loop in filter. Filter iterates through the array and return all the elements based on condition

var peopleIknow = [
  { name: "Steve", friend: true },
  { name: "Dan", friend: false },
  { name: "Bart", friend: true },
  { name: "Sarah", friend: false },
  { name: "Michelle", friend: false },
  { name: "Holly", friend: true }
];

var o = peopleIknow.filter(e=> e.friend );

console.log(o)

edited May 4, 2018 at 22:09

answered May 4, 2018 at 22:08

Muhammad Usman

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1 Comment

Satish Kumar Over a year ago

e.friend === true is not nesessary as e.friend itself is boolean.

CertainPerformance · Accepted Answer · 2018-05-04 22:07:02Z

Using a for loop inside a filter function defeats the purpose - try just using the filter function to iterate. You also shouldn't try to filter over an array before the array has been declared.

The first argument to the filter function is the item being iterated over, and you're only interested in the friend property, so you can extract only the friend property. If friend is true, then you want to return true to the filter function, so that it's included in your final array - else, return false. So, just return the friend property as is.

const peopleIknow = [
  { name: "Steve", friend: true },
  { name: "Dan", friend: false },
  { name: "Bart", friend: true },
  { name: "Sarah", friend: false },
  { name: "Michelle", friend: false },
  { name: "Holly", friend: true }
];

const trueFriends = peopleIknow.filter(({ friend }) => friend);
console.log(trueFriends);

Luca Kiebel · Accepted Answer · 2018-05-04 22:09:08Z

0

Don't run a for loop in your filter function. Filter is so easy to use. If the result of the function passed to filter is true it adds that element to the return value. This is what you are looking for!

var peopleIknow = [
  { name: "Steve", friend: true },
  { name: "Dan", friend: false },
  { name: "Bart", friend: true },
  { name: "Sarah", friend: false },
  { name: "Michelle", friend: false },
  { name: "Holly", friend: true }
];

var trueFriends = [];

//                                         only the friends where person.friend is truthy 
trueFriends = peopleIknow.filter(person => person.friend);

console.log(trueFriends);

answered May 4, 2018 at 22:09

Luca Kiebel

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Comments

Satish Kumar · Accepted Answer · 2018-05-04 22:16:23Z

0

You may use filter() as well as reduce() to do the same.

Here is using reduce() method. Both reduce and filter runs for the function once for each element of the array.

var trueFriends = [];
var peopleIknow = [
  { name: "Steve", friend: true },
  { name: "Dan", friend: false },
  { name: "Bart", friend: true },
  { name: "Sarah", friend: false },
  { name: "Michelle", friend: false },
  { name: "Holly", friend: true }
];
trueFriends = peopleIknow.reduce((acc,i) => {
  i.friend && acc.push(i);// same as if(i.friend) then push
  return acc;
},[]);
console.log(trueFriends);

edited May 4, 2018 at 22:16

answered May 4, 2018 at 22:07

Satish Kumar

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2 Comments

Luca Kiebel Over a year ago

While this code snippet may solve the problem, it doesn't explain why or how it answers the question. Please include an explanation for your code, as that really helps to improve the quality of your post. Remember that you are answering the question for readers in the future, and those people might not know the reasons for your code suggestion.

Satish Kumar Over a year ago

@Luca. When I answered, I just saw that there were 4 other answers just for a simple fix and with an explanation too.

Zeyad · Accepted Answer · 2018-05-04 22:20:27Z

0

You created filter and apply what the filter do in it, this code will work as you like.

var trueFriends = [];
var peopleIknow = [
      { name: "Steve", friend: true },
      { name: "Dan", friend: false },
      { name: "Bart", friend: true },
      { name: "Sarah", friend: false },
      { name: "Michelle", friend: false },
      { name: "Holly", friend: true }
    ];
    
   trueFriends = peopleIknow.filter(function(item){
      return item.friend});
    console.log(trueFriends)

edited May 4, 2018 at 22:20

answered May 4, 2018 at 22:10

Zeyad

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