Is there a reset button in JavaScript?

JavaScript is a widely used programming language that can be combined with HTML and CSS to make Web sites and Web applications more interactive and dynamic. However, when using JavaScript, you may encounter the need to reset the form, which is a common requirement. In this article, we will explore the reset button in JavaScript and how to use it.

First of all, it needs to be clear that the form element is one of the most important elements in HTML forms. It is used to capture user-entered data and submit it to the server for processing. In the form element, you can add buttons, including buttons, submit buttons, reset buttons, etc. Among them, the reset button is used to reset all data in the form to default values ​​or empty values.

In JavaScript, there are several ways to implement the reset button function. Below we will introduce these methods one by one.

1. Use the reset method of the form element

In JavaScript, the form element has a built-in method called reset(), which can be used to reset all inputs in the form fields and options. For example:

<form id="myForm">
  <input type="text" id="username" name="username" value="ABC">
  <select id="country" name="country">
    <option value="">请选择国家</option>
    <option value="China">中国</option>
    <option value="USA">美国</option>
  </select>
  <input type="reset" value="Reset">
</form>

<script>
  var myForm = document.getElementById("myForm");
  myForm.addEventListener("reset", function(event){
    console.log("表单已重置");
  });
</script>

In the above code, the form element contains an input field and a drop-down list box, as well as a reset type button. When the user clicks the reset button, the form element's reset() method is triggered, resetting all input fields and options in the form to their default or empty values. At the same time, the above JavaScript code also listens to the reset event of the form. When the form is reset, a message will be printed to the console.

2. Construct a new form and replace it with the old one

Another way to implement the reset button functionality is to construct a new form and replace it Old form. For example:

<form id="myForm">
  <input type="text" id="username" name="username" value="ABC">
  <select id="country" name="country">
    <option value="">请选择国家</option>
    <option value="China">中国</option>
    <option value="USA">美国</option>
  </select>
  <input type="button" value="Reset" onclick="resetForm()">
</form>

<script>
  function resetForm() {
    var oldForm = document.getElementById("myForm");
    var newForm = document.createElement("form");
    newForm.id = "myForm";
    oldForm.parentNode.replaceChild(newForm, oldForm);
  }
</script>

In the above code, the form element contains an input field and a drop-down list box, as well as a button type button. When the user clicks the reset button, the resetForm() function is called, where the old form element is first obtained, then a new form element is created using the createElement() method, and the new form element is replaced using the replaceChild() method Old form elements. This is equivalent to resetting the entire form.

It should be noted that when using this method, some form attributes, event handlers and other information may be lost, so it is only suitable for simple form reset.

3. Manually reset the value of the form element

The last way to implement the reset button function is to manually reset the value of the form element. For example:

<form id="myForm">
  <input type="text" id="username" name="username" value="ABC">
  <select id="country" name="country">
    <option value="">请选择国家</option>
    <option value="China">中国</option>
    <option value="USA">美国</option>
  </select>
  <input type="button" value="Reset" onclick="resetForm()">
</form>

<script>
  function resetForm() {
    var inputs = document.getElementById("myForm").getElementsByTagName("input");
    for(var i=0; i<inputs.length; i++) {
      switch(inputs[i].type) {
        case "text":
          inputs[i].value = "";
          break;
        case "checkbox":
        case "radio":
          inputs[i].checked = false;
          break;
        default:
          break;
      }
    }
    
    var selects = document.getElementById("myForm").getElementsByTagName("select");
    for(var i=0; i<selects.length; i++) {
      selects[i].selectedIndex = 0;
    }
  }
</script>

In the above code, the form element contains an input field and a drop-down list box, as well as a button type button. When the user clicks the reset button, the resetForm() function is called, which first obtains all input fields and drop-down list boxes of the form elements, and traverses each element to reset their values ​​to the default value or null value. . Specifically, for text boxes and password boxes, set their values ​​to empty; for radio buttons and check boxes, set their selected status to unchecked; for drop-down list boxes, set their selected items to First item.

It should be noted that if the form contains other types of form elements, such as text fields, password fields, image fields, etc., they need to be reset according to specific circumstances.

To sum up, there are many methods in JavaScript to reset the form. Among them, the reset() method that comes with the form element is the simplest and most direct. But if you need more flexibility in customizing the reset function, you can use the latter two methods. No matter which method is used, the need for form reset can be easily achieved and provide a better experience for users.

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