React Native Custom Multi Selector - Step 3

App.js

  selectPokemon(item) {
    if (!item.Choose) {
        const newArray = [...this.state.PokemonList];
        const replaceArray = {
            id: item.id,
            Name: item.Name,
            Avatar: item.Avatar,
            Choose: !item.Choose
        };
        newArray.splice(newArray.findIndex(ele => ele.id === item.id), 1, replaceArray);
        this.setState({ PokemonList: newArray });

        this.state.SelectedPokemon.push({
            id: item.id,
            Name: item.Name,
            Avatar: item.Avatar
        })

    } else {
        const newArray = [...this.state.PokemonList];
        const replaceArray = {
            id: item.id,
            Name: item.Name,
            Avatar: item.Avatar,
            Choose: !item.Choose
        };
        newArray.splice(newArray.findIndex(ele => ele.id === item.id), 1, replaceArray);
        this.setState({ PokemonList: newArray });

        const deleteArrayValue = [...this.state.SelectedPokemon];
        deleteArrayValue.splice(deleteArrayValue.findIndex(ele => ele === item.id), 1);
        this.setState({ SelectedPokemon: deleteArrayValue });
    }
  }

  onChoose() {
    this.setState({ 
        SavedPokemon : this.state.SelectedPokemon,
        MultiSelectPopup: false
    })
  }