Question

如何在铁形聚合物中实现addEventListener？

我已经按照本指南进行操作：iron-form

这是我的代码：

<form is="iron-form" method="get" action="/" id="eventsDemo">
  <paper-input name="name" label="Name" required auto-validate></paper-input>
  <paper-input name="password" label="Password" type="password" required auto-validate></paper-input>
  <paper-checkbox name="read" required>You must check this box</paper-checkbox><br>
  <paper-button raised onclick="_delayedSubmit(event)" disabled id="eventsDemoSubmit">
  <paper-spinner id="spinner" hidden></paper-spinner>Submit</paper-button>
  <paper-button raised onclick="_reset(event)">Reset</paper-button>
  <div class="output"></div>
</form>
<script>
  eventsDemo.addEventListener('change', function(event) {
    // Validate the entire form to see if we should enable the `Submit` button.
    eventsDemoSubmit.disabled = !eventsDemo.validate();
  });
  function _delayedSubmit(event) {
    spinner.active = true;
    spinner.hidden = false;
    eventsDemoSubmit.disabled = true;
    // Simulate a slow server response.
    setTimeout(function() {
      Polymer.dom(event).localTarget.parentElement.submit();
    }, 1000);
  }
  function _reset(event) {
    var form = Polymer.dom(event).localTarget.parentElement
    form.reset();
    form.querySelector('.output').innerHTML = '';
  }
  document.getElementById('eventsDemo').addEventListener('iron-form-submit', function(event) {
    spinner.active = false;
    spinner.hidden = true;
    eventsDemoSubmit.disabled = false;
    this.querySelector('.output').innerHTML = JSON.stringify(event.detail);
  });
</script>

我的表单ID＆events; eventsDemo＆＃39;没有定义，为什么？

Uncaught ReferenceError: eventsDemo is not defined

Answer 1

尚未在JS中声明class MainClass { public static void main(String[] args) { Runtime.getRuntime().addShutdownHook(new Thread() { @Override public void run() { org.apache.catalina.startup.Bootstrap("stop"); } }); org.apache.catalina.startup.Bootstrap("start"); } }变量。我看到你有一个eventsDemo的元素，但是它不会自动声明一个变量以便在id="eventsDemo"标记中使用。

要按标识符获取元素，您可以在<script>中使用document.getElementById或document.querySelector：

<script>

如何在铁形式聚合物中实现addEventListener

1 个答案: