Javascript OnClick before submit按钮

我有一个问题，在页面提交之前运行一些代码

当我将返回值更改为true以提交表单时，上面的代码不会运行。按照现在的方式，代码运行并刷新页面。我想传递一个真变量来提交表单，有什么想法吗

    function buildMessageC() {

    //Create an ePOS-Print Builder object
    var builder = new epson.ePOSBuilder();
    //Create a print document
    builder.addTextLang('en')
    builder.addTextSmooth(true);
    builder.addTextFont(builder.FONT_A);
    builder.addTextSize(1, 1);
    builder.addText(document.getElementById('receipt').textContent);
    builder.addFeedLine(1);
    builder.addCut(builder.CUT_FEED);
    //Acquire the print document
    var request = builder.toString();

    //Set the end point address
    var address = 'http://192.168.1.69/cgi-bin/epos/service.cgi?devid=counter_printer&timeout=10000';
    //Create an ePOS-Print object
    var epos = new epson.ePOSPrint(address);

    //Send the print document
    epos.send(request);

    return false;

表单按钮

        <sf:form onsubmit="return buildMessageC()">
            <input class="addToOrderButton button blue large expand" value="Place Order" name="_eventId_placeOrder" type="submit"/>
        </sf:form>

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您想运行该请求并提交表单吗？epos框架是否有某种完整的事件？是的。文档中的所有内容都以epos结尾。发送（请求）打印收据。如果该调用是异步调用，它需要有一个完整的方法才能知道何时提交表单。是否需要在表单标记中添加操作属性？（猜测，没有与epos合作）我更新了问题

   function doSubmit(){
    buildMessageC();
    return false;
}  gives me print out and reloads the same page not submiting the form                                                                                                             

   function doSubmit(){
    buildMessageC();
    return true;
} doesn't print yet submits the form