Vue resets child Component data on props update - vue.js

Question

I have child component, that has some internal data, that should not be changed from outside. But when I update prop from parent component, this internal data is reset.
Basically in example below, when we change title from outside, value is set back to empty ''. How can I make value persistent with Child component props update?
Child.vue
<template>
<div class="child">
<h2>{{title}}</h2>
<input type="text" :value="value" v-on:change="$emit('change', $event.target.value)">
</div>
</template>
<script>
export default {
props: {
title: {
default: 'Just title'
}
},
data() {
return {
value: ''
}
}
}
</script>
Parent.vue
<template>
<div class="parent">
<Child :title="title" v-on:change="processTitle($event)"></Child>
</div>
</template>
<script>
import Child from './Child';
export default {
data() {
return {
title: 'Title from parent'
}
},
methods: {
processTitle(value) {
this.title = value.reverse();
}
}
}
</script>

Answer 1

You are not setting the value data attribute, :value=value means that "if value changes, the input value should pick up that change". But value doesn't change. Use v-model instead if you want to keep it simple.
Vue.component("Child", {
props: {
title: {
default: 'Just title'
}
},
data() {
return {
value: ''
}
},
template: `
<div class="child">
<h2>{{title}}</h2>
<input type="text" v-model="value" v-on:change="$emit('change', $event.target.value)">
</div>
`
})
new Vue({
el: "#app",
data() {
return {
title: 'Title from parent'
}
},
methods: {
processTitle(value) {
this.title = value.split("").reverse().join("");
}
},
template: `
<div class="parent">
<child :title="title" v-on:change="processTitle($event)"></child>
</div>
`
})
<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.17/vue.js"></script>
<div id="app"></div>
EDIT
Also, if you want a continuous effect, don't use #change - use #input instead:
Vue.component("Child", {
props: {
title: {
default: 'Just title'
}
},
data() {
return {
value: ''
}
},
template: `
<div class="child">
<h2>{{title}}</h2>
<input type="text" v-model="value" v-on:input="$emit('change', $event.target.value)">
</div>
`
})
new Vue({
el: "#app",
data() {
return {
title: 'Title from parent'
}
},
methods: {
processTitle(value) {
this.title = value.split("").reverse().join("");
}
},
template: `
<div class="parent">
<child :title="title" v-on:change="processTitle($event)"></child>
</div>
`
})
<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.17/vue.js"></script>
<div id="app"></div>