Check if Array Contains an Object in JavaScript

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Borislav Hadzhiev

Last updated: Dec 26, 2022
9 min

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# Table of Contents

  1. Check if an Array contains an Object with Array.some()
  2. Check if an Array Contains an Object with Array.find()
  3. Check if an Array Contains an Object with Array.findIndex()
  4. Check if an Array Contains an Object with Array.filter()
  5. Check if an Array Contains an Object with Array.includes()
  6. Check if an Array Contains an Object using a for...of loop
  7. Check if an Array Contains an Object using a for loop
  8. Check if an Object is NOT contained in an array in JavaScript
  9. Check if a Value is NOT in an Array in JavaScript
  10. Check if a Value is NOT in an Array using indexOf

# Check if an Array contains an Object with Array.some()

To check if a JavaScript array contains an object:

  1. Use the Array.some() method to iterate over the array.
  2. Check if each object contains a property with the specified value.
  3. Array.some() will return true if the object is contained in the array.
index.js
const people = [
  {id: 1, name: 'John'},
  {id: 2, name: 'Adam'},
];

const isFound = people.some(element => {
  if (element.id === 1) {
    return true;
  }

  return false;
});

console.log(isFound); // 👉️ true

if (isFound) {
  // object is contained in the array
}

check if array contains object with array some

The function we passed to the Array.some() method gets called with each value (object) in the array.

If it returns a truthy value at least once, the Array.some method short-circuits and returns true.

On each iteration, we check if the current object has an id property with a value of 1.

If the condition is met, we return true, otherwise, we return false.

If the Array.some() method returns true, the object is contained in the array.

If you need to get the matching object, use the Array.find() method.

# Check if an Array Contains an Object with Array.find()

This is a three-step process:

  1. Use the Array.find() method to iterate over the array.
  2. Check if each object in contains a property with the specified value.
  3. Array.find() will return the object if the object is contained in the array.
index.js
const people = [
  {id: 1, name: 'John'},
  {id: 2, name: 'Adam'},
];

const person = people.find(element => {
  if (element.id === 1) {
    return true;
  }

  return false;
});

console.log(person); // 👉️ { id: 1, name: 'John' }

if (person !== undefined) {
  // 👉️ object is contained in the array
}

check if array contains object with array find

The function we passed to the Array.find() method gets called with each element in the array until it returns a truthy value or iterates over the entire array.

If the condition is met, the Array.find() method returns the corresponding array element, otherwise, it returns undefined.

There is an object with an id of 1, so the find() method returns the object.

You should use the Array.find() method instead of Array.some() when you need to access additional properties on the object.

If you need to get the index of the matching object, use the Array.findIndex() method.

# Check if an Array Contains an Object with Array.findIndex()

This is a three-step process:

  1. Use the Array.findIndex() method to iterate over the array.
  2. Check if each object contains a property with the specified value.
  3. The findIndex() method will return the index of the object in the array, or -1 if the object isn't in the array.
index.js
const people = [
  {id: 1, name: 'John'},
  {id: 2, name: 'Adam'},
];

const index = people.findIndex(element => {
  if (element.id === 1) {
    return true;
  }

  return false;
});

console.log(index); // 👉️ 0

if (index !== -1) {
  // 👉️ object is contained in the array
}

check if array contains object with array findindex

The Array.findIndex() method is very similar to the Array.find() method, but it returns the index of the element that satisfies the condition and not the element itself.

The Array.findIndex() method calls its callback function with each element in the array until a truthy value is returned or the values in the array are exhausted.

The Array.findIndex() method returns -1 if all calls of the callback function return a falsy value.

if you need to get all matching objects, use the Array.filter() method.

# Check if an Array Contains an Object with Array.filter()

This is a three-step process:

  1. Use the Array.filter() method to iterate over the array.
  2. Check if each object contains a property with the specified value.
  3. The Array.filter() method will return an array containing the objects that meet the condition (if any).
index.js
const people = [
  {id: 1, name: 'John'},
  {id: 2, name: 'Adam'},
];

const filteredArray = people.filter(element => {
  if (element.id === 1) {
    return true;
  }

  return false;
});

console.log(filteredArray); // 👉️ [ { id: 1, name: 'John' } ]

if (filteredArray.length > 0) {
  // 👉️ object is contained in the array
}

check if array contains object with array filter

The function we passed to the Array.filter method gets called with each element in the array.

The method iterates over the entire array and doesn't short-circuit if the condition is met, so it could return more than one object if multiple objects meet the condition.

We check if each element (object) in the array contains an id property with a value of 1. If the new array isn't empty, there are matching objects.

Note that the Array.filter() method returns an array with all of the elements that meet the condition.

If we had multiple objects with an id equal to 1, all of them would get included in the new array.

index.js
const people = [
  {id: 1, name: 'John'},
  {id: 2, name: 'Adam'},
  {id: 1, name: 'Bobby'},
];

const filteredArray = people.filter(element => {
  if (element.id === 1) {
    return true;
  }

  return false;
});

// 👇️ [ { id: 1, name: 'John' }, { id: 1, name: 'Bobby' } ]
console.log(filteredArray);

if (filteredArray.length > 0) {
  // 👉️ object is contained in the array
}

There are multiple objects in the array with an id of 1, so they all get included in the new array.

You can also use the Array.includes() method to check if an object is contained in an array.

# Check if an Array Contains an Object with Array.includes()

This is a three-step process:

  1. Store the object in a variable.
  2. Push the object into the array.
  3. Use the Array.include() method to check if the object is contained in the array.
index.js
const obj = {id: 2, name: 'Adam'};

const people = [{id: 1, name: 'John'}];

people.push(obj);

if (people.includes(obj)) {
  // 👇️ this runs
  console.log('The object is contained in the array');
} else {
  console.log('The object is NOT contained in the array');
}

check if array contains object with array includes

Note that this approach only works if you have access to the object that was pushed into the array.

The Array.includes() method returns true if the supplied value is contained in the array and false otherwise.

However, when we use the includes() method with an object, it checks by reference and not by value.

In other words, the method looks for the same object that it contains (the same location in memory).

This wouldn't work if you have an object that has the same key-value pairs but has a different reference.

index.js
const people = [{id: 1, name: 'John'}];

// 👇️ false
console.log(people.includes({id: 1, name: 'John'}));

The code sample returns false because the object we passed to the Array.includes() method has a different reference, even though it has the same key-value pairs.

Only use the includes() method to check if an array contains an object if you have access to the same object (the same location in memory) that is stored in the array.

index.js
const obj = {id: 2, name: 'Adam'};

const people = [{id: 1, name: 'John'}];

people.push(obj);

if (people.includes(obj)) {
  // 👇️ this runs
  console.log('The object is contained in the array');
} else {
  console.log('The object is NOT contained in the array');
}

You can also use a for...of loop to check if an array contains an object.

# Check if an Array Contains an Object using a for...of loop

This is a three-step process:

  1. Use a for...of loop to iterate over the array.
  2. Check if each object has a property with the specified value.
  3. If the condition is met, set a boolean variable to true.
index.js
const people = [
  {id: 1, name: 'John'},
  {id: 2, name: 'Adam'},
];

let isContained = false;

for (const obj of people) {
  if (obj.id === 1) {
    isContained = true;
    console.log(obj); // 👉️ { id: 1, name: 'John' }
    break;
  }
}

console.log(isContained); // 👉️ true

We declared a new variable and initialized it to false.

The for...of statement is used to loop over iterable objects like arrays, strings, Map, Set and NodeList objects and generators.

On each iteration, we check if the current object has an id property with a value of 1.

If the condition is met, we set the isContained variable to true and use the break statement to exit the loop.

The break statement helps us avoid iterating over the array needlessly once we've found the matching object.

You can also use a basic for loop to check if an array contains an object.

# Check if an Array Contains an Object using a for loop

This is a three-step process:

  1. Use a for loop to iterate over the array.
  2. Check if the object at the current index has a property with the specified value.
  3. Set a boolean variable to true if the condition is met.
index.js
const people = [
  {id: 1, name: 'John'},
  {id: 2, name: 'Adam'},
];

let isContained = false;

for (let index = 0; index < people.length; index++) {
  if (people[index].id === 1) {
    isContained = true;
    console.log(people[index]); // 👉️ { id: 1, name: 'John' }
    break;
  }
}

console.log(isContained); // 👉️ true

We used a basic for loop to iterate over the array.

On each iteration, we check if the object at the current index has an id property with a value of 1.

If the condition is met, we set the isContained variable to true and exit the for loop.

Which approach you pick is a matter of personal preference. I'd use the Array.some() method as I find it quite direct and intuitive.

# Check if an Object is NOT contained in an array in JavaScript

To check if an object is not contained in an array:

  1. Use the Array.every() method to iterate over the array.
  2. Check if each object doesn't have a property equal to the specified value.
  3. The every() method will return true if the object is not contained in the array.
index.js
const arr = [
  {id: 1, name: 'Alice'},
  {id: 2, name: 'Bobby'},
  {id: 3, name: 'Carl'},
];

const notInArray = arr.every(obj => {
  return obj.id !== 4;
});

console.log(notInArray); // 👉️ true

if (notInArray) {
  // 👇️ this runs
  console.log('The object is NOT contained in the array');
} else {
  console.log('The object is contained in the array');
}

The function we passed to the Array.every method gets called with each element (object) of the array.

On each iteration, we check if the current object doesn't have an id property with a value of 4.

If all invocations of the callback function return a truthy value, then the Array.every() method returns true, otherwise, false is returned.

If the callback function we passed to the Array.every() method returns a falsy value, then Array.every() short-circuits also returning false.

# Check if a Value is NOT in an Array in JavaScript

Use the logical NOT (!) operator to negate a call to the includes() method to check if a value is not contained in an array.

The expression will return true if the value is not contained in the array and false otherwise.

index.js
const arr = ['bobby', 'hadz', 'com'];

if (!arr.includes('XYZ')) {
  // 👇️ this runs
  console.log('✅ value is not in array');
} else {
  console.log('⛔️ value is in array');
}

We used the logical NOT (!) operator to negate a call to the Array.includes() method to check if the specified value is not contained in the array.

The Array.includes() method returns true if the supplied value is contained in the array and false otherwise.

Since we want to check if the value is NOT contained in the array, we have to negate (!) the result.

Here are some examples of using the logical NOT (!) operator.

index.js
console.log(!true); // 👉️ false
console.log(!false); // 👉️ true

console.log(!'hello'); // 👉️ false
console.log(!''); // 👉️ true
console.log(!null); // 👉️ true

You can imagine that the logical NOT (!) operator:

  1. converts the value to a boolean
  2. flips the boolean
When you negate a falsy value, the operator returns true, in all other cases it returns false.

Falsy values are: null, undefined, "" empty string, NaN (Not a number), 0 and false.

If you have to check if a value is not contained in an array often, define a reusable function.

index.js
function notInArray(arr, value) {
  return !arr.includes(value);
}

const arr = ['bobby', 'hadz', 'com'];

console.log(notInArray(arr, 'bobby')); // 👉️ false
console.log(notInArray(arr, 'XYZ')); // 👉️ true
console.log(notInArray(arr, 'com')); // 👉️ false

if (notInArray('XYZ')) {
  // 👇️ this runs
  console.log('The value is NOT in the array');
} else {
  console.log('The value is in the array');
}

The notInArray function takes an array and a value as parameters and returns true if the value is not in the array and false otherwise.

An alternative approach is to use the Array.indexOf method.

# Check if a Value is NOT in an Array using indexOf

If the indexOf method returns -1, the value is not contained in the array.

index.js
const arr = ['bobby', 'hadz', 'com'];

if (arr.indexOf('XYZ') === -1) {
  // 👇️ this runs
  console.log('✅ value is not in array');
} else {
  console.log('⛔️ value is in array');
}

The Array.indexOf method returns the index of the first occurrence of the supplied value in the array.

If the value is not contained in the array, the method returns -1.

Our if statement checks if the method returned -1.

If it did, then the value is not contained in the array.

You can define a reusable function if you have to do this often.

index.js
function notInArray(arr, value) {
  return arr.indexOf(value) === -1;
}

const arr = ['bobby', 'hadz', 'com'];

console.log(notInArray(arr, 'bobby')); // 👉️ false
console.log(notInArray(arr, 'XYZ')); // 👉️ true
console.log(notInArray(arr, 'com')); // 👉️ false

if (notInArray('XYZ')) {
  // 👇️ this runs
  console.log('The value is NOT in the array');
} else {
  console.log('The value is in the array');
}

The function takes an array and a value as parameters and returns true if the value is not contained in the array and false otherwise.

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