How to add only 1 time the same item in the cart ? (Javascript)

Question

How would you add only 1 time the same item in the cart?

import React, { Component } from "react";
import * as S from './styles'

//Components
import ImgCar from '../src/components/imgs/car.svg';

class Car extends Component {

  state = {
    carAdd: [],
    car: [
      {
        id: 0,
        name: "Jetta",
        assembler: "Volkswagen",
        price: 144000,
        type: "Sedan",
        btnDisabled: false
      },
      {
        id: 1,
        name: "Polo",
        assembler: "Volkswagen",
        price: 70000,
        type: "Hatch",
        btnDisabled: false
      },
      {
        id: 2,
        name: "T-Cross",
        assembler: "Volkswagen",
        price: 123000,
        type: "SUV",
        btnDisabled: false
      }
     
    ]
  }

  funcBtnAdd = (event) => {
    const check = this.state.car.filter(item => item.id == event.id);
    event.btnDisabled = true;
    console.log(check)
    this.setState({
      carAdd: this.state.carAdd.concat(check)
    })
  }

Answer 1

If checking is the car to be added, would do the following:

  funcBtnAdd = (event) => {
    const check = this.state.car.filter(item => item.id == event.id);
    event.btnDisabled = true;

    const isCarAlreadyAdded = this.carAdd.some(car => car.id === check.id);
    
    if (!isCarAlreadyAdded) {
      this.setState(prevState => ({
        carAdd: [...prevState, check]
      }))
    }
  }

Explanation: The function some returns true if the condition passed is true. Then, it checks whether in the array of cars already added (carAdd) there is already the new car to be inserted. If yes, the value of the isCarAlreadyAdded variable will be true, and the state will not be updated.