How to prevent repeated update of nested DOM

[saindo]

<div v-if="a>0"> <span>{value}</span> </div>
By runtime code: a=2; value='xxx', SPAN will be updated twice, by both "a" and "value". Is there any workaround to re-render SPAN only once, if I have to update both "a" and "value"? Is there any way to cancel re-rendering in beforeUpdate()?
BTW, I'm just putting this in a simple way. Actually, in my case, the "value" is a long list rendered by v-for. So each time the long list is updated twice.
TKS.

[LinusBorg]

By runtime code: a=2; value='xxx', SPAN will be updated twice,

That synchronous code would result in one update. updates are batched on the next tick.

[saindo]

right. Your point sheds some light on this shit hill of mine. Actually through debugging, I see the list is updated twice, unnecessarily. So it must be some asynchronous change, in another direction than where I was looking. TKS.