WebSocket 在代码中返回 undefined 但不在控制台中 [英] WebSocket returns undefined in code but not in console

问题描述

我正在努力理解这里发生了什么......

I'm struggling to understand what's happening here...

我在 192.168.1.64:81 上有一个 websocket 服务器

I have a websocket server on 192.168.1.64:81

我需要使用此 javascript 将数据从网页发送到套接字:

I need to send data to the socket from a web page using this javascript:

window.onload = function() {
    var connection = new WebSocket("ws://"+location.hostname+":81", ['arduino']);
    connection.onopen = function() {
        connection.send('Connect ' + new Date());
    };
    connection.onerror = function(error) {
        console.log('WebSocket Error ', error);
    };
    connection.onmessage = function(e) {
        console.log('Server: ', e.data);
    };

    function sendData() {
        var data="#"+joystick.deltaX()+","+joystick.deltaY();
        connection.send(data);
    }};

现在是这样的:如果我打开 js 控制台(在 firefox 中)，我会看到连接未定义"错误......但是如果我将行复制粘贴到控制台:

Now this is what happens: if I open the js console (in firefox) I see the "connection is undefined" error... but if I copy-paste to the console the line:

    var connection = new WebSocket("ws://"+location.hostname+":81", ['arduino']);

socket 被正确定义，更新程序开始通过 socket 正确传输数据！！

the socket gets defined correctly and the updater begins streaming data correctly through the socket!!

我错过了什么?我应该知道一些众所周知的问题吗?

What am I missing? Should I be aware of some well known issue?

推荐答案

以下函数使用了 connection 变量，但是变量超出了作用域，因为 connection 是使用 var(本地)关键字定义:

The following functions use the connection variable, but the variable is out of scope, because connection is defined using the var (local) keyword:

connection.onopen = function() {
    connection.send('Connect ' + new Date());
};
function sendData() {
    var data="#"+joystick.deltaX()+","+joystick.deltaY();
    connection.send(data);
}};

或者将`connection 定义为全局值:

Either define `connection as a global value:

connection = new WebSocket("ws://"+location.hostname+":81", ['arduino']);

或者使用内部绑定/引用:

Or use an internal binding / reference:

connection.onopen = function(e) {
    e.target.send('Connect ' + new Date());
};
sendData = function() {
    var data="#"+joystick.deltaX()+","+joystick.deltaY();
    this.send(data);
}.bind(connection);

否则将连接初始化为全局并像这样分配 onload:

Otherwise initialize connection as a global and assign onload like this:

    var connection;
window.onload = function() {
        connection = new WebSocket("ws://"+location.hostname+":81", ['arduino']);
        connection.onopen = function() {
            connection.send('Connect ' + new Date());
        };
        connection.onerror = function(error) {
            console.log('WebSocket Error ', error);
        };
        connection.onmessage = function(e) {
            console.log('Server: ', e.data);
};};

这篇关于WebSocket 在代码中返回 undefined 但不在控制台中的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！