Let's talk about the common understanding of v-show and V-IF in Vue project

Enthusiastic citizen Lao Guo 2020-11-10 15:10:51
let talk common understanding v-show

stay Vue On the project , Sometimes we need to show and hide the page elements ,Vue The framework provides instructions for conditional rendering v-show and v-if.

So what's the difference , Let's take a look at the official v-show and v-if A comparative explanation of :

Official explanation

v-if yes “ real ” Conditional rendering , Because it ensures that the event listeners and child components within the condition block are properly destroyed and rebuilt during the switch .

v-if It's also inert : If the condition is false at the initial render , And do nothing —— Until the condition is true for the first time , Before the condition block is rendered .

by comparison ,v-show It's much simpler —— Whatever the initial conditions are , Elements are always rendered , And simply based on CSS Switch .

Generally speaking ,v-if There is higher switching overhead , and v-show There is a higher initial rendering overhead . therefore , If you need to switch very frequently , Then use v-show good ; If conditions rarely change at run time , Then use v-if good .

Next we'll explain through the code v-show and v-if The difference between



<div>v-show Show and hide </div>
<div v-show="show"> I'm going to show and hide elements </div>


export default {
data() {

return {




The elements hide , But we F12,Elements You can see that the elements are still , Just added display:none; attribute .



<div>v-if Show and hide </div>
<div v-if="show"> I'm going to show and hide elements </div>


export default {
data() {

return {

 Talk about it Vue On the project commonly used v-show and v-if The understanding of the

The same effect , The elements hide , But we F12,Elements The elements in it are gone .

Sum up their differences
1. methods :
v-if It's dynamic DOM Add or remove... From the tree DOM Elements ;
v-show By setting DOM Elemental display The style attribute controls the display and concealment ;
2. The build process :
v-if The switch has a partial compilation / Uninstallation process , Properly destroy and rebuild the internal event monitor and sub components during the handover process ;
v-show It's simply based on css Switch ;
3. Compile conditions :
v-if It's inert. , If the initial condition is false , And do nothing ; Local compilation starts only when the condition first becomes true ( The compilation is cached ? After the compilation is cached , And then, when switching, local unloading is performed );
v-show Under any conditions ( Is the first condition true ) All compiled , Then it's cached , and DOM Element retention ;
4. Performance consumption :
v-if Higher switching consumption ;
v-show There is a higher initial render cost ;
5. Use scenarios :
v-if Suitable operating conditions are unlikely to change ;
v-show Suitable for frequent switching .

If you want to switch nodes frequently , Use v-show( No matter what true perhaps false The initial rendering will be done , Adopted thereafter css To control the display hide , Therefore, the switching cost is relatively small , The initial cost is high ), If you don't need to switch nodes frequently , Use v-if( Because of lazy loading , For the initial false when , Does not render , But because it's by adding and removing dom Elements to control display and hide , So the initial rendering costs less , Switching overhead is relatively large .
In this paper, the source : Youth code farmer WeChat official account
edit : Biao Vatican interaction

本文为[Enthusiastic citizen Lao Guo]所创,转载请带上原文链接,感谢

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