How to check for email duplication from array in JavaScript?

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Have two emails and trying to check if it matches anything in my data array which is an array of emails.

Thought the below would return true or false but it seems to be not working:

 const email1 = test.emailAddress.value;
 const email2 = test2.emailAddress.value;

 data.every(({ email }) => email.value === email1 || email.value === email2);

You can filter your data with the matched array of two emails like so:

const data = [
  {email: ''},
  {email: ''},
  {email: ''}

const email1 = ''
const email2 = ''

const matched = data.filter(({ email }) => [email1, email2].includes(email));

3 Ways to Find Duplicate Elements in an Array - Java, the time complexity of O(n^2) and only exists for the academic purpose. Another alternate method to find duplicate values in an array using JavaScript is using reduce method. Using reduce method you can set the accumulator parameter as an empty array. On each iteration check if it already exists in the actual array and the accumulator array and return the accumulator.

According to your code, the .every method checks if every email in the data array is either email1 or email2, if at least one of the emails in the data array fails the condition, the .every method returns false. Which means that the .every method is not suitable for what you want to achieve.

var exists = data.some(({email}) => [email1, email2].includes(email))

Thats with the assumption that data is a array of objects that contain email attribute. If data is simply an array of email strings, then it should be

var exists = data.some(email => [email1, email2].includes(email))

Check if an array contains duplicate values, How do you find the duplicate number on a given integer array JavaScript? You want to check if each of the values in the array are unique (check for duplicates) or if the array itself is unique compared to another array? – David says reinstate Monica Oct 29 '13 at 10:48 Edited the question to be more specific.

Unless you provide your data it is hard to figure out what is going on. But you can useincludes to check if an element is present in an array or not.

The includes() method determines whether an array includes a certain element, returning true or false as appropriate.

if( data.includes(email1) || data.includes(email2)){ // ||  && depending upon your needs
   //do something

Check if an array contains duplicates in JavaScript, I wanted to write a javascript function which checks if array contains duplicate values or not. I have written the following code but its giving answer as "true" always. If you were using Java instead of JavaScript, the associative array would be a HashMap instead. When we loop over the initial array, we use the array element value as our count key and if it doesn’t exist, we give it a value to represent it is now defined.

JavaScript array: Find duplicate values in a array, In this post, we will see how to check if an array contains any duplicate elements in JavaScript. 1. Using ES6 Set. The Set object, introduced in the ES6, can be  Given an array populated with numbers as a function parameter, produce a resulting array which contains any duplicates number from the array. For example, given the array [ 1, 2, 4, 4, 3, 3, 1, 5, 3 ] it should return [1, 4, 3]. For extra bonus points return a sorted array.

Calculate If Duplicates Exist In An Array Using JavaScript, JavaScript exercises, practice and solution: Write a JavaScript program to find duplicate values in a JavaScript array. Basically, we iterate over the array and, for each element, check if the first position of this element in the array is equal to the current position. Obviously, these two positions are different for duplicate elements. Using the 3rd ("this array") parameter of the filter callback we can avoid a closure of the array variable:

Removing duplicates from an array with vanilla JavaScript, Use JavaScript to calculate if duplicate values exist in a single array. going to look into the different ways of finding duplicates in an array. Solution: No, it's me who did the mess. My function was checking for duplicates, but didn't reset after that. Here's the fixed version of your second for