Find duplicate values in objects with Javascript

Question

I\'ve been trying to work out a problem I\'m having. I have an array with objects in it, like this:

var array = [
  {
    name: \"Steven Smith\",
    Country         


        

Answer 1

I'm a little late to the party but this might help someone who's facing the same problem, as it is, I believe, an easier to understand solution:

let duplicates = [];
array.forEach((el, i) => {
  array.forEach((element, index) => {
    if (i === index) return null;
    if (element.name === el.name && element.Age === el.Age) {
      if (!duplicates.includes(el)) duplicates.push(el);
    }
  });
});
console.log("duplicates", duplicates);

Two things might be tricky to understand:

• with forEach you can provide a second argument that will be an index. This is to make sure we don't compare the same two array entries with each other (if (i === index) return null; -> to abort the forEach)
• !duplicates.includes ("if not duplicates includes) checks before adding an element to the duplicates array if it's already there. Since {} === {} is false in JS, this will not be a problem with "equal" objects already in the duplicates array, but will simply avoid adding the same element twice in one forEach loop

Edit: An even nicer solution would be this:

const duplicates = array
    .map((el, i) => {
        return array.find((element, index) => {
            if (i !== index && element.name === el.name && element.Age === el.Age) {
                return el
            }
        })
    })
    .filter(x => x)
console.log("dupliactes:", duplicates)

It has no side effects and all logic is in one if statement. The filter is needed to sort out undefined instances.