每次我单击提交时，jQuery都会不断发布一条额外的消息 [英] jQuery keeps posting an extra message each time I click submit

问题描述

我的jQuery代码表现得很奇怪.每当我单击提交"时，它都会不断发布同一封邮件的额外副本.例如:

My jQuery code is acting really weird. It keeps posting an extra copy of the same message each time I click on submit. For example:

Hello 3
Hello 3
Hello 3
Hello 2
Hello 2
Hello 

任何人都知道为什么会这样吗?到目前为止，这是我的代码:

Anyone have an idea why this is happening? Here is my code so far:

jQuery(function ($) {
    var socket = io.connect();
    var $messageForm = $('#sendmessage');
    var $messageTitle = $('#title');
    var $messageBox = $('#message');
    var $chat = $('#chat');

    $messageForm.click(function (e) {
        if ($.trim($("#title").val()).length === 0) {
            alert('You must provide valid input');
            $messageTitle.val('');
            $messageBox.val('');
            return false;
        }
        if ($.trim($("#message").val()).length === 0) {
            alert('You must provide valid input');
            $messageTitle.val('');
            $messageBox.val('');
            return false;
        } else {
            e.preventDefault();
            socket.emit('send message', '<b>' + $messageTitle.val() + '</b>' + '&nbsp;-&nbsp;' + $messageBox.val());
            $messageTitle.val('');
            $messageBox.val('');
        }

        socket.on('new message', function (data) {
            $chat.prepend(data + "<br/>");
        });
    });
});

推荐答案

此函数在每次调用时都会注册一个事件处理程序.因为您是在click事件中调用它的，所以每次单击时都需要注册一个新的事件处理程序.这些都是在队列中管理的，因此，每次单击按钮时，它将在事件处理程序中运行额外的时间.

This function here registers an event handler every time it's called. Because you're calling it in the click event, every time you click, you register a new event handler. These are managed in a queue, and thus, it will run through the event handler an extra time with each button click.

socket.on('new message', function (data) {
            $chat.prepend(data + "<br/>");
        });

解决方案是将其移到click事件之外.

The solution is to move it outside of the click event.

jQuery(function ($) {
    var socket = io.connect();
    var $messageForm = $('#sendmessage');
    var $messageTitle = $('#title');
    var $messageBox = $('#message');
    var $chat = $('#chat');

    $messageForm.click(function (e) {
        if ($.trim($("#title").val()).length === 0) {
            alert('You must provide valid input');
            $messageTitle.val('');
            $messageBox.val('');
            return false;
        }
        if ($.trim($("#message").val()).length === 0) {
            alert('You must provide valid input');
            $messageTitle.val('');
            $messageBox.val('');
            return false;
        } else {
            e.preventDefault();
            socket.emit('send message', '<b>' + $messageTitle.val() + '</b>' + '&nbsp;-&nbsp;' + $messageBox.val());
            $messageTitle.val('');
            $messageBox.val('');
        }
    });
    socket.on('new message', function (data) {
        $chat.prepend(data + "<br/>");
    });   
});

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