Question 220619 in Javascript Question posted in
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How to get a Key name from a Javascript Object?

Consider the below object and I’m trying to console the below-mentioned output.

const jonas = {
  firstName: 'Jonas',
  lastName: 'Schmedtmann',
  age: 2037 - 1991,
  job: 'teacher',
  friends: ['Micheal', 'Peter', 'Steven']
};
console.log(`${jonas.firstName} has ${jonas.friends.length} friends, and his best friend is ${jonas.friends[0]}.`);

Now, instead of hardcoding friends in the console, how do I access the key name "friends" from the object?

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3

Answers


  1. 0

    You can use Bracket Notation :

    const jonas = {
    firstName: 'Jonas',
    lastName: 'Schmedtmann',
    age: 2037 - 1991,
    job: 'teacher',
    friends: ['Micheal', 'Peter', 'Steven']
};

const keyName = 'friends';
console.log(`${jonas.firstName} has ${jonas[keyName].length} ${keyName}, and his best ${keyName} is ${jonas[keyName][0]}.`);
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  2. 0

    You can use the following element

    Object.keys(jonas)

    that return an array of Keys of the object so you can take the value using

    Object.keys(jonas)[4]
That return the key "friends"
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  3. 0

    You could try a for loop:

    const jonas = {
  firstName: 'Jonas',
  lastName: 'Schmedtmann',
  age: 2037 - 1991,
  job: 'teacher',
  friends: ['Micheal', 'Peter', 'Steven']
};

let hasFriends = false;

for (const key in jonas) {
if (key === 'friends') {
  hasFriends = true;
  break;
  }
}

if (hasFriends) {
  console.log(`${jonas.firstName} has ${jonas.friends.length} friends, and his 
best friend is ${jonas.friends[0]}.`);
} else {
  console.log(`${jonas.firstName} does not have any friends.`);
}

    or even try:

    for (const key in jonas) {
  console.log(`${key} has ${Array.isArray(jonas[key]) ? jonas[key].length : jonas[key]}.`);
}
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