Detect change to modelValue in Vue 3 - vuejs3

Question

Is there a way to detect change to modelValue in a custom component? I want to push the change to a wysiwyg editor.
I tried watching modelValue but emitting update for modelValue triggered that watch, which created circular data flow.
Code:
export default {
props: ['modelValue'],
watch: {
modelValue (val) {
this.editor.editor.loadHTML(val)
}
},
mounted () {
this.editor.editor.loadHTML(val)
this.editor.addEventListener('trix-change',
(event) => this.$emit('update:modelValue', event.target.value))
}
}
<TextEditor v-model="someHtml"></TextEditor>

Answer 1

In VueJS v3, the event name for custom v-model handling changed to 'update:modelValue'.
You can listen to these events like this: v-on:update:modelValue="handler"
For a more complete example, lets assume you have a Toggle component with these properties/methods:
...
props: {
modelValue: Boolean,
},
data() {
return {
toggleState: false,
};
},
methods: {
toggle() {
this.toggleState = !this.toggleState;
this.$emit('update:modelValue', this.toggleState);
}
}
...
You can use that Toggle component:
<Toggle v-model="someProperty" v-on:update:modelValue="myMethodForTheEvent"/>
As a side note, you could also v-model on a computed property with a setter; allowing you to internalise your state changes without using the update:modelValue event. In this example, it assumes you v-model="customProperty" on your custom Toggle component.
computed: {
customProperty: {
get() {
return this.internalProperty;
},
set(v) {
this.internalProperty = v;
console.log("This runs when the custom component 'updates' the v-model value.");
},
}
},

Answer 2

I had the same problem and solved it using a slight tweak to the way you call the watch function:
setup(props) {
watch(() => props.modelValue, (newValue) => {
// do something
})
}
Hence, the important thing is to add () => props.modelValue instead of just putting props.modelValue as the first argument of the watch function.

Answer 3

try that:
watch: {
...
modelValue: function(val) {
console.log('!!! model value changed ', val);
},
...