我有一个提供各种不同HTML页面的Node服务器。在其中一页中有一个表格。单击表单后，node server.js文件中的端点将使用表单数据。相同的HTML页面包含一个
元素，我希望在提交表单时修改其文本内容。我在线上看过各种教程，展示了如何使用document.getElementById('predictionText').innerHTML = prediction;使用内联JavaScript动态设置文本的值。如何使用Node和外部js实现此目标？
下面是我的代码：
<!DOCTYPE html>
<html>
<head>
<link rel="stylesheet" type="text/css" href="css/styles.css">
</head>
<body class="bodyContent">
<p>This is the predictor page -- it will hold a form for the user to input relevant data to.</p>
<section class="active" id="navigationBarSection">
<ul>
<li><a href="index">Home</a></li>
<li><a href="predictor">Predictor</a></li>
<li><a href="how_it_works">How it Works</a></li>
<li><a href="about_us">About Us</a></li>
</ul>
</section>
<section id="predictorUserInputSection">
<form action="/post_data_to_predictor_algorithm" method="POST" id="attributeInputForm">
<input class="textInput" required name="averageAreaIncome" placeholder="Average Area Income" />
<input class="textInput" required name="averageAreaNumberOfRooms" placeholder="Average Area Number of Rooms" />
<input class="textInput" required name="averageAreaHouseAge" placeholder="Average Area House Age" />
<input class="textInput" required name="averageAreaNumberOfBedrooms" placeholder="Average Area Number of Bedrooms"/>
<input class="textInput" required name="areaPopulation" placeholder="Area Population"/>
<button id="submitButton">Submit</button>
</form>
</section>
<section id="predictionResultsSection">
<p id="predictionText"><font size="6">here </p>
</section>
<script src="server.js"></script>
</body>
</html>
应更新文本的节点服务器：
//jshint esversion:8
//adding all required dependencies/packages
const express = require('express');
const path = require('path');
const fs = require("fs");
const bodyParser = require('body-parser'); //for parsing post requests
const request = require('request') //for making HTTP requests
//specifies that this app will be using express.
const app = express();
//middleware for processing POST requests a bit easier.
app.use(bodyParser.urlencoded({extended: false}));
//static AWS EC2 instance server port. Edit with caution.
const serverPort = 5001;
const FLASK_SERVER_LOCAL_ENDPOINT = "http://localhost:5000/predictPrice";
//Allow the use of static files in project directory
app.use('/js', express.static(__dirname + '/js'));
app.use('/html', express.static(__dirname + '/html'));
app.use('/css', express.static(__dirname + '/css'));
app.use('/node_modules', express.static(__dirname + '/node_modules'));
app.use('/resources', express.static(__dirname + '/resources'));
const XMLHttpRequest = require("xmlhttprequest").XMLHttpRequest;
//Handle all root requests.
app.get("/", function(req, res) {
res.sendFile(path.resolve("index.html"));
});
app.get("/index", function(req, res) {
res.sendFile(path.resolve("index.html"));
});
app.get("/predictor", function(req, res) {
res.sendFile(path.resolve("html/predictor.html"));
});
app.get("/how_it_works", function(req, res) {
res.sendFile(path.resolve("html/how_it_works.html"));
});
app.get("/about_us", function(req, res) {
res.sendFile(path.resolve("html/about_us.html"))
});
//HERE IS THE PROBLEM
app.post("/post_data_to_predictor_algorithm", (req, res) => {
//update prediction label in the UI:
console.log("Updating label!");
document.getElementById('predictionText').innerHTML = "received user response!";
});
[运行服务器时，提交表单时收到以下错误：
ReferenceError: document is not defined
at app.post (/Users/vismarkjuarez/Documents/Github/RealEstatePriceEstimator/server.js:90:3)
at Layer.handle [as handle_request] (/Users/vismarkjuarez/Documents/Github/RealEstatePriceEstimator/node_modules/express/lib/router/layer.js:95:5)
at next (/Users/vismarkjuarez/Documents/Github/RealEstatePriceEstimator/node_modules/express/lib/router/route.js:137:13)
at Route.dispatch (/Users/vismarkjuarez/Documents/Github/RealEstatePriceEstimator/node_modules/express/lib/router/route.js:112:3)
at Layer.handle [as handle_request] (/Users/vismarkjuarez/Documents/Github/RealEstatePriceEstimator/node_modules/express/lib/router/layer.js:95:5)
at /Users/vismarkjuarez/Documents/Github/RealEstatePriceEstimator/node_modules/express/lib/router/index.js:281:22
at Function.process_params (/Users/vismarkjuarez/Documents/Github/RealEstatePriceEstimator/node_modules/express/lib/router/index.js:335:12)
at next (/Users/vismarkjuarez/Documents/Github/RealEstatePriceEstimator/node_modules/express/lib/router/index.js:275:10)
at /Users/vismarkjuarez/Documents/Github/RealEstatePriceEstimator/node_modules/body-parser/lib/read.js:130:5
at invokeCallback (/Users/vismarkjuarez/Documents/Github/RealEstatePriceEstimator/node_modules/raw-body/index.js:224:16)
如果要在表单的同一页面中更新DOM元素，则必须构建一个动态表单，因为带有action =“ / destination”的标准表单会将您发送到新页面，或者在无法编写的页面上重建现有页面在文档上，原因节点不知道DOM。您需要Jquery或直接使用xhr。例如：
// Build a single field dynamic Form:
<div id="myForm">
<input type="text" id="textA"></input>
<button type="submit" onclick="getElements()"> Submit </button>
</div>
// The element that need be updated.
<section id="predictionResultsSection">
<p id="predictionText"><font size="6">here </p>
</section>
// Get the "form" field value.
function getElements() {
var tA = document.getElementById("textA");
formSubmit(tA.value)
}
// Do the request
function formSubmit(sendData) {
var xhttp = new XMLHttpRequest();
xhttp.open("POST", "http://localhost/post_data_to_predictor_algorithm");
xhttp.send(sendData);
// Receive the response from server on this.responseText var
xhttp.onreadystatechange = function () {
if (this.readyState == 4 && this.status == 200) {
document.getElementById('predictionText').innerHTML = this.responseText;
}
};
}
// Server side
app.post("/post_data_to_predictor_algorithm", (req, res) => {
//do your logic and send the response
res.send(yourResponse) // the onreadystatechange will hadle this on responseText
});