Check if Array Contains an Object in JavaScript

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

To check if a JavaScript array contains an object:

1. Call the Array.some method passing it a function
2. The function should check whether the identifier of the object is equal to a specific value and return true if it is
3. Array.some will return true is the conditional check is satisfied at least once

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// Supported in IE 9-11
const people = [
  {id: 1, name: 'John'},
  {id: 2, name: 'Adam'},
];

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

console.log(isFound); // 👉️ true

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

The function we passed to the Array.some method will get called with each value of the array.

In our conditional check we verify if the identifier property of the object is equal to a specific value, if it is, then we know that the object exists in the array.

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

To check if a JavaScript array contains an object:

1. Call the Array.find method passing it a function
2. The function should check whether the identifier of the object is equal to a specific value and return true if it is
3. Array.find will return the object if the conditional check is satisfied at least once

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// Not Supported in IE 6-11
const people = [
  {id: 1, name: 'John'},
  {id: 2, name: 'Adam'},
];

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

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

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

The function we passed to the Array.find method gets called with each array element, until it returns a truthy value or iterates over all array elements.

In the code example, the condition returns true, therefore the find method returns the object.

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

To check if a JavaScript array contains an object:

1. Call the Array.findIndex method, passing it a function
2. The function should check whether the identifier of the object is equal to a specific value and return true if it is
3. The Array.findIndex method will return the index of the object that satisfies the condition and -1 if none do

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// Not supported in IE 6-11
const people = [
  {id: 1, name: 'John'},
  {id: 2, name: 'Adam'},
];

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

console.log(index); // 👉️ 0

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

The Array.findIndex method is very similar to the Array.find method, but returns the index of the element that satisfies the conditional check, 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.

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

To check if a JavaScript array contains an object:

1. Call the Array.filter method, passing it a function
2. The function should check whether the identifier of the object is equal to a specific value and return true if it is
3. The Array.filter method will return an array containing the objects that satisfy the conditional check (if any)

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// Supported in IE 9-11
const people = [
  {id: 1, name: 'John'},
  {id: 2, name: 'Adam'},
];

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

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

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

The Array.filter method gets invoked with every element in the array, which is different than the other methods, which would short circuit if their callback function returned a truthy value.

For each element of the array, we verify if its unique identifier matches a specific value, if it does, we know that the object is contained in the array.