How to remove object in array of objects with matching values

Question

I want to check my array for objects with matching values, if they match remove the object with the lowest index as that will be the one is "older"

I had success using this method for removing duplicate objects in the array, but when i get to specific values of those objects i'm not sure

someFunction() {
  let cart = this.state.currentUser.cart
    const newCartArray = cart.filter((light, index) => {
      return index === cart.findIndex(obj => {
          obj.use === light.use
      })
    })
  cart = newCartArray
}

do you have some data to illustrate the problem?

Nina Scholz
– Nina Scholz

2019-10-11 18:53:40 +00:00
Commented Oct 11, 2019 at 18:53 — Nina Scholz
– Nina Scholz, Commented Oct 11, 2019 at 18:53

Nina Scholz · Accepted Answer · 2019-10-11 19:06:41Z

You could take a Map and store the last object with a wanted key and get as result only the last stored objects.

var array = [{ id: 1, index: 0 }, { id: 2, index: 1 }, { id: 3, index: 2 }, { id: 2, index: 3 }, { id: 3, index: 4 }, { id: 1, index: 5 }, { id: 4, index: 6 }, { id: 5, index: 7 }],
    result = Array.from(array.reduce((m, o) => m.set(o.id, o), new Map).values());

console.log(result);

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If you like to keep the original order, you could check the same object reference for filtering.

var array = [{ id: 1, index: 0 }, { id: 2, index: 1 }, { id: 3, index: 2 }, { id: 2, index: 3 }, { id: 3, index: 4 }, { id: 1, index: 5 }, { id: 4, index: 6 }, { id: 5, index: 7 }],
    map = array.reduce((m, o) => m.set(o.id, o), new Map),
    result = array.filter(o => o === map.get(o.id));

console.log(result);

.as-console-wrapper { max-height: 100% !important; top: 0; }

Derek Lawrence · Accepted Answer · 2019-10-11 19:06:28Z

0

let cart = this.state.currentUser.cart;
let index = cart.indexOf(light);
if( index != -1) {
    cart.splice( index,1);
}

or if you need to check the .use

let cart = this.state.currentUser.cart;
for( let i =0; i < cart.length; i++) {
    if( cart[i].use === light.use) {
        cart.splice(i,1);
        break;
    }
}

edited Oct 11, 2019 at 19:06

answered Oct 11, 2019 at 18:59

Derek Lawrence

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Comments

Andre Nuechter · Accepted Answer · 2019-10-11 19:22:47Z

0

You could filter out all the items that have subsequent items match the relevant property, like so:

const newCartArray = cart.filter((light, i, array) => {
  return !array.slice(i + 1).some(obj => obj.use === light.use);
})

answered Oct 11, 2019 at 19:22

Andre Nuechter

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Comments

marzelin · Accepted Answer · 2019-10-11 19:28:11Z

0

This should work:

someFunction() {
  let cart = this.state.currentUser.cart
    const newCartArray = cart.filter((light, index) => {
      return cart.slice(index + 1).findIndex(obj => {
          obj.use === light.use
      }) === -1;
    })
  cart = newCartArray
}

answered Oct 11, 2019 at 19:28

marzelin

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