Array.push() Element if does not exist using JavaScript

If you want to add an element to an array in JavaScript, but only if it doesn’t already exist in the array, there are a few different approaches you can take. Here are some options for checking if an element exists in an array and adding it if it doesn’t:

Method 1: Array.includes() and Array.push()

One way to check if an element exists in an array is to use the Array.includes() method. This method returns true if the specified element is found in the array, and false if it is not. You can use this method in conjunction with the Array.push() method to add the element to the array if it doesn’t already exist:

const arr1 = ['a', 'b', 'c', 'd'];
const value1 = 'e';

if (!arr1.includes(value1)) {
  arr1.push(value1);
}

This approach works well with primitive data types such as strings, numbers, and booleans. If you’re working with objects, however, you’ll need to use a different method to check if the element exists in the array.

Method 2: Array.findIndex() and Array.push()

To check if an element exists in an array of objects, you can use the Array.findIndex() method. This method returns the index of the first element in the array that meets a specific condition, or ‘-1’ if no element meets the condition.

Here’s an example of using Array.findIndex() and Array.push() to add an element to an array of objects:

const arr2 = [{id: 1}, {id: 2}];
const value2 = {id: 3};

const index = arr2.findIndex(object => object.id === value2.id);

if (index === -1) {
  arr2.push(value2);
}

In this example, we use the Array.findIndex() method to find the index of the first element in the array that has an id property equal to 3. If no such element is found, the findIndex() method returns -1.

[Fixed]: Cannot find module ‘commander’ error in Node.js

We then use an if statement to check if the index is equal to -1. If it is, we know that the element doesn’t exist in the array, so we can add it using the Array.push() method.

Method 3: Array.indexOf() and Array.push()

If you’re working with primitive data types, you can also use Array.indexOf() method to check if an element exists in an array. This method returns the index of the first occurrence of the specified element in the array, or -1 if the element is not found.

Here’s an example of using Array.indexOf() and Array.push() to add an element to an array:

const arr3 = ['a', 'b', 'c', 'd'];
const value3 = 'e';

if (arr3.indexOf(value3) === -1) {
  arr3.push(value3);
}

Like the Array.includes() method, Array.indexOf() is well-suited for working with primitive data types.

Method 4: Lodash .includes() and .push()

If you’re using the Lodash library, you can use the .includes() and .push() methods to check if an element exists in an array and add it if it doesn’t.

Here’s an example of using these methods:

const arr4 = ['a', 'b', 'c', 'd'];
const value4 = 'e';

if (!_.includes(arr4, value4)) {
  _.push(arr4, value4);
}

The .includes() method works the same way as the native Array.includes() method, and the .push() method works the same way as the native Array.push() method.

Method 5: JavaScript Unless Statement

If you prefer a more concise syntax, you can use a JavaScript “unless” statement to add an element to an array if it doesn’t already exist. An ‘unless statement‘ is the opposite of an if statement: it executes the code block if the condition is false.

Here’s an example of using an ‘unless statement’ to add an element to an array:

const arr5 = ['a', 'b', 'c', 'd'];
const value5 = 'e';

unless (arr5.includes(value5)) {
  arr5.push(value5);
}

In this example, we use the ‘unless statement’ to check if the value5 element is not included in the arr5 array. If it is not, we add it using the Array.push() method.

Keep in mind that the ‘unless statement‘ is not a native JavaScript feature, so you’ll need to use a transpiler or a polyfill to use it in your code.

Conclusion Array.push() Element if does not exist using JavaScript

There are several different ways you can check if an element exists in an array and add it if it doesn’t in JavaScript.

Depending on your needs and preferences, you can use the native Array.includes(), Array.findIndex(), or Array.indexOf() methods, or the Lodash .includes() and .push() methods.

You can also use a JavaScript “unless” statement to achieve the same result with a more concise syntax.

If you are still getting the error please let us know in the comments section, I would love to solve your problem.

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