[Vue warn]: Duplicate keys detected: x. This may cause an update error. How to prevent adding item which has already been added via method

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I have a v-autocomplete that loops a list of users. I then add them to a new list via a btn. How to I stop and alert that a user has already been added by comparing the dup key?

<v-autocomplete
    v-model="event.user"
    :items="usersData"
    label="Seach speaker list"
    :search-input.sync="searchUser"
    return-object
    item-value="id"
    item-text="name"
></v-autocomplete>

My method to addSpeaker is:

addSpeaker() {
    const newSpeaker = {
        id: this.event.user.uid,
        name: this.event.user.name,
    }
    this.speakers.push(newSpeaker)
    this.event.user = ''
},
removeSpeaker(id) {
    this.speakers = this.speakers.filter(speaker => speaker.id !== id)
}

Is there a check I can do here to prevent a user being added if it already has been?

29 thoughts on “[Vue warn]: Duplicate keys detected: x. This may cause an update error. How to prevent adding item which has already been added via method”

  1. Check if the user exists by using id. If the user exists then show an error, else add the user:

    addSpeaker () {
  const newSpeaker = {
    id: this.event.user.uid,
    name: this.event.user.name,
  }

  let doesUserExists = false;

  for (let i = 0; i < this.speakers.length; i++) {
    if (this.speakers[i].id === newSpeaker.id) {
      // Show an error that the user does already exists

      doesUserExists = true;

      break;
    }
  }

  if (!doesUserExists) {
    this.speakers.push(newSpeaker);
  }

  this.event.user = ''
},
    Reply

  2. you can use findIndex

    addSpeaker() {
  const newSpeaker = {
    id: this.event.user.uid,
    name: this.event.user.name
  };
  const check = this.speakers.findIndex(x => x.name == this.event.user.name) === -1;
  check && this.speakers.push(newSpeaker);
  this.event.user = "";
}
    Reply

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