在Javascript / HTML中将Firebase数据显示为数组

Question

Edit: Object.keys(snapshot.val())[0] returns "-LfL-eVLT1QtZw-LAvpS" which is the randomly assigned Firebase name. But how do I display the "text" property of that?

The code below works pretty well. I can hit the Submit Data button and it'll push the data to the Firebase, but I'm having trouble displaying it. I want to display the data in an HTML list, but Firebase returns a nested object, not an array, and I don't know what to do with it.

I've attached a screenshot so it's clear what my code is doing. JSON.stringify is very promising - it shows all the data, so I know it's actually there and communicating properly with the database. But it's obviously not usable in any sense. I need to know what I can do so I can apply a .map() to part of my code and make it work, but I'm coming up empty after hours of trying things.

Object.keys(snapshot) I thought would convert the object into an array, but I can't tell what that's doing at all.

import React, {useState} from 'react'
import fire from './fire'
import './App.css'

const App = () => {
  let [messageList, setMessageList] = useState(fire.database().ref('messages'))

  const handleSubmit = (e) => {
    e.preventDefault()
    //fire.database().ref('messages').push( document.querySelector("#message-input").value );
    fire.database().ref('messages').push({ text: document.querySelector("#message-input").value, id: document.querySelector("#message-input").value })
  }

  var ref = fire.database().ref("messages")
  var fireArray = [fire.database().ref("messages")]

  ref.on("value", function(snapshot) {
    document.querySelector("#value").innerHTML = JSON.stringify(snapshot)
    document.querySelector("#snapshotval").innerHTML = snapshot.val().text
    document.querySelector("#snapshot").innerHTML = snapshot
    document.querySelector("#messages").innerHTML = Object.keys(snapshot)
  }, function (error) {
    console.log("Error: " + error.code);
  });

  return(
    <section>
    <form onSubmit={handleSubmit}>
      <input type="text" id="message-input"></input>
      <button>Submit Data</button>
    </form>
    <h2>JSON.stringify(snapshot)</h2>
    <p id="value"></p>
    <h2>snapshot.val()</h2>
    <p id="snapshotval"></p>
    <h2>snapshot</h2>
    <p id="snapshot"></p>
    <h2>Object.keys(snapshot)</h2>
    <p id="messages"></p>
    </section>
  )
}

export default App;

Answer 1

You can use JSX to display data:

<p id="value">{JSON.stringify(messageList)}</p>

messageList would be the result of the Firebase response:

ref.on("value", function(snapshot) {
    setMessageList(snapshot)
  }, function (error) {
    console.log("Error: " + error.code);
  });

More information: https://reactjs.org/docs/introducing-jsx.html