freeCodeCamp/guide/english/certifications/javascript-algorithms-and-data-structures/basic-data-structures/check-if-an-object-has-a-property/index.md

title

title
Check if an Object has a Property

Check if an Object has a Property

Basic Solution:

let users = {
  Alan: {
    age: 27,
    online: true
  },
  Jeff: {
    age: 32,
    online: true
  },
  Sarah: {
    age: 48,
    online: true
  },
  Ryan: {
    age: 19,
    online: true
  }
};

function isEveryoneHere(obj) {
  if (
    obj.hasOwnProperty('Alan') && obj.hasOwnProperty('Jeff') &&
    obj.hasOwnProperty('Sarah') && obj.hasOwnProperty('Ryan')
  ) {
    return true;
  }
  return false;
}

Code Explanation

• Checks whether object contains all users by using the hasOwnProperty method for each name with the && operator to return a true or false value.

Advanced Solution:

let users = {
  Alan: {
    age: 27,
    online: true
  },
  Jeff: {
    age: 32,
    online: true
  },
  Sarah: {
    age: 48,
    online: true
  },
  Ryan: {
    age: 19,
    online: true
  }
};

function isEveryoneHere(obj) {
  return [
    'Alan',
    'Jeff',
    'Sarah',
    'Ryan'
  ].every(name => obj.hasOwnProperty(name));
}

Code Explanation

• Uses an array with all of the names which should be present in the object.
• The every method is used to validate all of names used in conjunction with the hasOwnProperty method result in a value of true being returned during each iteration.
• If at least one name is not found using the hasOwnProperty method, the every method returns false.

Relevant Links

• Array.prototype.every