Explain how to submit a form using javascript

With the continuous advancement of Web technology, the development of dynamic Web websites has attracted more and more attention. JavaScript, as a client-side scripting language, provides good interaction and response capabilities for Web applications. Among them, submitting a form is one of the most basic functions of JavaScript.

This article will explain to you how to use JavaScript to submit a form, mainly from the following aspects:

1. The basic structure and attributes of the form

2. Using JavaScript Obtain form data

3. Modify form data and submit the form

4. Preprocessing and verification of form data

1. Basic structure and attributes of the form

First, we need to understand the basic structure and attributes of the form. The basic structure of the form is as follows:

<form action="xxx" method="xxx" enctype="xxx">
    表单控件
    <input type="xxx" name="xxx">
    ...
</form>

Among them, the action attribute indicates the URL address of the form submission, and the method attribute indicates the request method. Generally, GET## is used. # or POST, the enctype attribute indicates how to encode the form data. As for form controls, we can divide them into two categories: form elements and form fields.

Form elements include:

d5fd7aea971a85678ba271703566ebfd, 221f08282418e2996498697df914ce4e, 4750256ae76b6b9d804861d8f69e79d3, bb9345e55eb71822850ff156dfde57c8 , 2e1cf0710519d5598b1f0f14c36ba674, etc.

Form fields group and identify form controls, as shown in the following code:

<fieldset>
    <legend>表单域名称</legend>
    ...
    表单控件
    <input type="xxx" name="xxx">
    ...
</fieldset>

2. Use JavaScript to obtain form data

Obtaining form data is the key to submitting the form Steps, we can obtain form data through the following methods:

// 获取表单对象
var formObj = document.forms[0]; // 或者 document.forms["form_name"];

// 获取表单控件值
var inputObj = formObj.elements["input_name"];
var inputValue = inputObj.value;

// 获取选择框选中的值
var selectObj = formObj.elements["select_name"];
var selectValue = selectObj.options[selectObj.selectedIndex].value;

// 获取多行文本框的值
var textareaObj = formObj.elements["textarea_name"];
var textareaValue = textareaObj.value;

Among them, the

querySelector and querySelectorAll methods can also obtain elements and element collections:

var inputObj = document.querySelector('[name="input_name"]');
var selectObj = document.querySelector('[name="select_name"]');
var textareaObj = document.querySelector('[name="textarea_name"]');

3. Modify the form data and submit the form

After obtaining the form data, we can modify and process them. For example:

inputObj.value = "new_value";
textareaObj.value = textareaObj.value.toUpperCase();
selectObj.options[1].selected = true;

When the form data is processed, we need to submit it to the server. At this time, we need to use the

submit() method:

formObj.submit();

If you need to confirm or verify before submitting the form, you can use the

onsubmit event:

formObj.onsubmit = function () {
    // 验证表单数据是否合法
    ...
    // 如果验证失败，则返回false取消表单提交
    if (!isValid) {
        return false;
    }
    // 验证成功，提交表单
    return true;
}

4. Preprocessing and verification of form data

For data preprocessing and verification before form submission, we can use the following techniques:

// 对数据进行预处理
function preProcessData(formData) {
    formData.username = formData.username.toUpperCase();
    formData.password = formData.password.toLowerCase();
    ...
}

// 对数据进行验证
function validateFormData(formData) {
    if (!formData.username) {
        alert("请填写用户名！");
        return false;
    }
    if (!formData.password) {
        alert("请填写密码！");
        return false;
    }
    ...
    return true;
}

// 表单提交事件
formObj.onsubmit = function () {
    // 获取表单数据
    var formData = {
        username: inputUsername.value,
        password: inputPassword.value,
        ...
    };
    // 预处理表单数据
    preProcessData(formData);
    // 验证表单数据是否合法
    if (!validateFormData(formData)) {
        return false;
    }
    // 提交表单
    formObj.submit();
    return true;
}

The above is the JavaScript form submission basic process. In actual development, we need to perform corresponding processing and verification based on the structure and data of the form based on specific business needs to achieve a more complete and robust form submission function.

The above is the detailed content of Explain how to submit a form using javascript. For more information, please follow other related articles on the PHP Chinese website!