You could consider using a store like Vuex in this case.

1. After parent component did the transformation, dispatch action and mutate global store property.
2. In child 2 component, watch to the changes to this store property and then update it's input model

You can use v-model with components. Docs

That said, I would do something like this: Codepen

<field v-model="text"></field>
<field v-model="processedText"></field>

and then use watchers

watch: {
  text(text) {
    this.processedText = this.process(text);
  },
  processedText(text) {
    this.text = this.process(text);
  }
}

Of course there's probably more than one way to do it, but this seems like the shortest route :)

Thanks to all answers you guys provided. I've learned some new tricks from these advises. But I'd like to make a clarification and provide the best(for my opinion) choice!

For the start, my method:

1. In the child component: Note, that I'm using VueJs2, so the configuration of CHILD might be different to use v-model. For inputs inside children we set: @input="$emit('input', $event.target.value)" v-bind:value="value", where value is a defined prop;
2. In the parent component: We don't need to set watchers. The problem of this decision(which is provided in vch's answer) is that it might be the root of infinity recursion inside parent's component. So we could just listen for input events inside children components, like this: @input="someValueChanged">. And we could even have a two-way listener field inside parent, by just using v-model on our custom components: v-model="some value".

The pros of my methods are clear: we have universal component for ANY input type. We can make a custom listeners by listening directly to emitted events. And we can put a needed modifiers, like .lazy on those custom inputs. There are no disadvanatages tbh, or I haven't found them yet.

vch's answer: Cool method, I've tried it, but it seems to be badly recursive inside parents component. Your codepen works, but in my case(VueJS2) it seems to be broken.. But I've started from your method and just removed useless watchers and added event listeners.

Pavan's answer: Again, working method. We could really use storage for such case, but I see sort of disadvantages here:

1. We use not an out-of-box extension - VueX, which have to be installed. I'm fan of built-in methods tbh;
2. We can't provide separated logic for every input - we'll have to make custom component for each mechanism, cuz they have to listen to different storage variables.

Thx you all! It was very useful!