CODEWITHSUNDEEP
javascriptarraysforeachjavascript-objects
Gerard Way
Gerard Way

Reputation: 91

Find a property (which is stored as a string in a variable) in an array of objects

I have an array of objects which store the data of different 'pupils'.

var pupils = [
{
    id: 0,
    name: 'will'
},
{
    id: 1,
    name: 'megan'
}
];

I want to create a function called 'findPupil' which takes three parameters: the property you know, the value you know it to be and the property you want to find.

Say you know that the pupil you are looking for has an id of 1 but you don't know their name. In this case, you would call the function like this:

var name = findPupil('id', 1, 'name'); // should now store 'Megan' as a string

Here is the function I have written:

function findPupil(property, value, find) {
pupils.forEach(function(pupil) {
    if(pupils[pupil][`${property}`] === value) {
      return pupils[pupil][`${find}`];
    }
  });
}

Calling this function returns the following: 

Error: Cannot read property 'id' of undefined

How do I make this function work?

Upvotes: 0

Views: 51

Answers (4)

AbdulaziAlswaji
AbdulaziAlswaji

Reputation: 31

    var pupils = [
    { id: 0, name: 'will' },
    { id: 1, name: 'megan' }
];

function findPupil(property, value, find) {
    var find_value = '';
    for (var i = 0; i < pupils.length; i++) {
        if (find_value == '') {
            Object.keys(pupils[i]).forEach(function (key) {
                if (key == property && pupils[i][key] == value) {
                    find_value = pupils[i][find];
                }
            });
        } else {
            break;
        }
    }
    console.log(find_value);
    return find_value;
}

var name = findPupil('id', 1, 'name');

Upvotes: 0

swapnesh
swapnesh

Reputation: 26732

Most of your code is correct except for the part of your if statement. Please find working example -

var pupils = [{
    id: 0,
    name: 'will'
  },
  {
    id: 1,
    name: 'megan'
  }
];

function findPupil(property, value, find) {
  let result
  pupils.forEach(function(pupil) {
    if (pupil[property] === value) {
      result = pupil[find];
    }
  });
  return result
}

var name = findPupil('id', 1, 'name');

console.log(name)

Upvotes: 0

Tyler Roper
Tyler Roper

Reputation: 21672

You could use .find() for that.

var pupils = [{id: 0, name: 'will'},{id: 1,name: 'megan'}];

function getByPropertyAndValue(knownProp, knownValue, desiredProperty) {
  let pupil = pupils.find(p => p[knownProp] === knownValue); //Find pupil by property and value
  return pupil && pupil[desiredProperty]; //Return the value, or undefined if not found
}

console.log(getByPropertyAndValue("id", 1, "name"));

Upvotes: 0

Ori Drori
Ori Drori

Reputation: 191986

Use Array.find() to find an object with the property you know, or a default if an object is not found. Extract the find property from the object:

const pupils = [{"id":0,"name":"will"},{"id":1,"name":"megan"}];

const findPupil = (property, value, find) =>
  (pupils.find(o => o[property] === value) || {})[find];

const name = findPupil('id', 1, 'name');

console.log(name);

Upvotes: 2

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