Removing duplicate values from array

Question

I'm adding several id's to an array when a checkbox is checked.

<input type="checkbox" name="vehicle2" onClick={() => this.addEvcGroupToArray(item.stations.map((item, key) => { return (item.stationID) }))}

This is the function that adds the ids to the array

     addEvcGroupToArray(id) {
        console.log("group_id ",id);
        var stationId = {};
        id.map((item, key) => {
            stationId = {
                stationId: item
            }
        })
        var evcGroupIdArray = this.state.stationIdArray.concat(stationId);
        this.setState({ stationIdArray: evcGroupIdArray })
    }

For example console.log("group_id ",id); outputs an array of ids like ["8"] (Here it's just one id,but this can be any number of ids). I want to prevent adding the same id's if the user click on the checkbox again.

I tried something like this using Set. But it did not work. How can i do this?

  addEvcGroupToArray(id) {
    console.log("group_id ",id);
    var stationId = {};
    id.map((item, key) => {
        stationId = {
            stationId: item
        }
    })
    var evcGroupIdArray = this.state.stationIdArray.concat(stationId);
    var uniqueArray = [...new Set(evcGroupIdArray)];
    this.setState({ stationIdArray: uniqueArray })
}

I am not familiar with React, however,why do you use map without assiging id.map? — StepUp
– StepUp, Commented Dec 23, 2019 at 13:01

Süleyman GÜNDÜZ · Accepted Answer · 2019-12-23 13:08:19Z

1

First initialize an array instead of an object like

let stationId = [];

After try adding this instead of adding id.map

id.forEach(item => {
  if (!this.state.stationIdArray.some(item => item === id)) {
   stationId.push(item);
 } 
})

and set the state

this.setState({ stationIdArray: [...stationIdArray, stationId] });

I hope it helps.

answered Dec 23, 2019 at 13:08

Süleyman GÜNDÜZ

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Comments

Mosè Raguzzini · Accepted Answer · 2019-12-23 13:08:51Z

1

map already returns an array, it is not recommended to use it to loop through values although you can do it.

const myArr = [
  {stationId: 3},
  {stationId: 1},
  {stationId: 2},
  {stationId: 3},
  {stationId: 3},
];


const result = [];
const map = new Map();
for (const item of myArr) {
if(!map.has(item.stationId)){
    map.set(item.stationId, true);    // set any value to Map
    result.push({
        stationId: item.stationId
    });
}
}
console.log(result)

answered Dec 23, 2019 at 13:08

Mosè Raguzzini

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Comments

Mario · Accepted Answer · 2019-12-23 13:32:55Z

0

Try cleaning id array just before going into the rest of the logic

addEvcGroupToArray (id) {
  console.log("group_id ", id);
  const clean = new Set(id); // <- remove duplicated ids
  var stationId = {};
  clean.map((item, key) => {
    stationId = {
      stationId: item
    };
  });
  var evcGroupIdArray = this.state.stationIdArray.concat(stationId);
  this.setState({ stationIdArray: evcGroupIdArray });
};

answered Dec 23, 2019 at 13:32

Mario

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Comments

ascripter · Accepted Answer · 2019-12-23 13:38:14Z

0

lodash _.uniqueBy can be applied on evcGroupIdArray.

_.uniqBy(evcGroupIdArray, 'stationId');

edited Dec 23, 2019 at 13:38

ascripter

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answered Dec 23, 2019 at 13:29

rav211

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Comments

Siva Kondapi Venkata · Accepted Answer · 2019-12-23 16:25:07Z

0

How about this?

function addEvcGroupToArray(id) {
    console.log("group_id ",id);
    // Get the current state id array
    const { stationIdArray } = this.state;
    // Append new id array
    const uniqueArray = [...new Set([...stationIdArray, ...id])];
    this.setState({ stationIdArray: uniqueArray })
}

answered Dec 23, 2019 at 16:25

Siva Kondapi Venkata

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