Question

So, I was working with React Native and found a very silly problem which I can't seem to get my head around. I have declared an array of objects (storeVar here) with some hardcoded value. When I try to loop through it using the javascript map function I get only the value only at the first index. The code is below -

import React, { Component } from 'react';
import {
  AppRegistry,
  StyleSheet,
  Text,
  View,
  TextInput,
  ScrollView,
  AsyncStorage,
  TouchableOpacity
} from 'react-native';

import Note from './note.js'

// -------------------------------------------------------------------------


const storeVar = [
    {
        'd' : '',
        'n' : 'Hello'
    },
    {
        'd' : '',
        'n' : 'Awesome'
    },
];

export default class reactNativePractise extends Component {
    constructor(props) {
    super(props);
    this.state = {
        noteArray : [
            {
                'date' : '',
                'note' : ''
            }
        ],
    };
}

componentDidMount() { this.onLoad(); }

onLoad = async()=> {
    storeVar.map(async(value, index) => {
        try {
            var d = new Date();
            // const storedVal = [await AsyncStorage.getItem(storeVar[index].n)];
            alert("Key is : " + JSON.stringify(storeVar[index-1].n, null, 4));

            // this.state.noteArray.push( {date :d.getFullYear() + "/" + (d.getMonth()+1) + "/" + d.getDate(), note : storedVal[index]} );
        }
        catch(error) { alert('Error' + error) }
    });
}

Only Hello is displayed and not the text Awesome. Any help would be greatly appreciated.

Answer 1

请勿使用index-1，请使用

JSON.stringify(storeVar[index].n, null, 4));

该索引将从0开始，因此-1的{{1}}将导致0，并且无法访问 -1th -1的元素，当索引变为array且1时，它将1 - 1打印Hello（0索引元素）。

Javascript | React Native map function not working properly

1 个答案: