Home > Article > Web Front-end > vue input changes values before and after
vue input changes values before and after
- WBOYOriginal
- 2023-05-11 12:35:071139browse
Vue is a popular JavaScript framework that makes it easy to create responsive components. In WEB development, input boxes in components are one of the most common elements. In many scenarios, developers need to track the value of an input box and process it. In this article, we will discuss how to handle the modified values of input boxes in Vue.
Listening to the input box
Vue provides a variety of ways to monitor the value of the input box. The most common way is to use v-model. The v-model directive implements two-way binding, which means that modifications to the input box will be reflected in the data attributes in the component instance, and when the value of the data attribute changes, the input box will also Automatically update the corresponding value.
The following is a simple example that demonstrates how to use v-model to monitor the value of a text input box:
<template>
<div>
<label for="username">用户名:</label>
<input id="username" v-model="username">
<p>用户名: {{ username }}</p>
</div>
</template>
<script>
export default {
data() {
return {
username: ""
};
}
};
</script>In the above example, we use v-model binds a text input box and maintains a username data attribute in the component instance. When the user enters a value in the input box, the username data attribute will be automatically updated, and the difference expression {{ username }} in the template will also be updated accordingly.
Record the value of the input box before and after modification
In some scenarios, we need to know the value of the input box before and after modification. For example, in a form, we want to be able to track the changes made by the user and save these changes to a changes array for subsequent use.
In Vue, we can use watch to monitor changes in data attributes. When the value of a data attribute changes, we can use the handler function to perform some operations.
We can use the following code to record the before and after modification values of a single input box:
<template>
<div>
<label for="username">用户名:</label>
<input id="username" v-model="username">
<p>用户名: {{ username }}</p>
<pre v-text="JSON.stringify(changes)">
In the above code, we record by adding a new changes array. Each modification of the input box. We have slightly modified the handler function in the watch option, now it will be triggered when the value of the input box changes. When the new value is not equal to the old value, we store the previous value and the next value in the form of objects in the changes array.
Record the values of multiple input boxes
In actual development, we usually need to monitor the values of multiple input boxes. In this case, we can use an object with the same format to store all input box changes. The attribute name in the object is the ID or name of the input box, and the attribute value is an object that contains the value before and after the input box is modified.
<template>
<div>
<label for="username">用户名:</label>
<input id="username" v-model="formData.username">
<p>用户名: {{ formData.username }}</p>
<label for="email">邮箱:</label>
<input id="email" v-model="formData.email">
<p>邮箱: {{ formData.email }}</p>
<pre v-text="JSON.stringify(changes)">
In the above code, we maintain the values of multiple input boxes by adding a new formData object in the data method. We also record all changes by adding a new changes object.
We modified the handler function in the watch option so that it now traverses the formData object. When it detects that the value of an input box has changed, it will check the changes object to see if the input box already exists, and set the before and after property values. If the input box does not exist in the changes object, a new attribute will be added.
We also set the deep property of the watch option to true, which will deeply monitor the properties of the formData object , so that when the value in the input box is nested in the formData object, the data can be observed correctly.
Summary
In this article, we discussed how to handle the modified values of the input box in Vue. We saw how to use watch to monitor changes in data properties, and how to record changes to input boxes into an object. In actual development, this technology is very useful and can help us track all changes in the form in real time.
The above is the detailed content of vue input changes values before and after. For more information, please follow other related articles on the PHP Chinese website!