Vue watch automatically detects data changes in real-time rendering method, vuewatch

Vue watch automatically detects data changes in real-time rendering method, vuewatch

This article describes how vue watch automatically detects data changes in real-time rendering:

First, make sure that watch is an object and must be used as an object.

The object has a key and a value.

Key: the guy you want to monitor, for example, $ route. This is to monitor route changes. Or a variable in data.
The value can be a function: it is the function to be executed when the guy you monitor changes. This function has two parameters: the first is the current value, and the second is the changed value.

The value can also be a function name. However, this function name must be enclosed in single quotes.

The third case is amazing.

The value is an object that includes options: There are three options.

1. The first handler: its value is a callback function. That is, the function to be executed when listening for changes.
2. The second is deep: The value is true or false; check whether the listener is listened in depth. (The attribute value of the object cannot be monitored during the listener, and the value of the array can be heard .)
3. The third is immediate: The value is true or false; check whether the handler function is executed with the current initial value.

Watch instance

You can use this. $ set or vm. set to dynamically change the data that has been rendered on the page (add, delete) and re-render the data.

Sometimes you need to dynamically change a data or value, and then perform other processing operations (such as display, hide, add, or delete) based on the value you change, the following code is used as an example:

Here is an example of a Tab:

Create a Tab component page in the vue Project

<Template >{{ index }}< div> <div @ click = "showFun (0)"> Tab1 </div> <div @ click = "showFun (1) "> Tab2 </div> <div @ click =" showFun (2) "> Tab3 </div> <div v-if =" index = 0 "> cont1 </div> <div v-if =" index = 1 "> cont1 </div> <div v-if =" index = 2 "> cont1 </div> </template> <script> export default {data () {return {index: 0 // index }}, watch: {// real-time index detection (idx) {// monitors index changes in real time. console. log (idx) // here you can perform other operations based on the idx value }}, methods: {showFun (idx) {this. index = idx }}</script>

Watch allows you to customize a listener. This method is most useful when you need to perform asynchronous or overhead operations when data changes

Let me take another search example:

<Template> <input v-model = "value"/> // search box </template> <script> export default {data () {return {value: ''// value }}, watch: {value (val) {// monitors data changes in real time this. wat_fun (val) }}, methods: {wat_fun (val) {// you can call the console of the search api here. log (val) }}</script>

Here are two simple examples to help you ~ We also hope that you can support the customer's home.