Sometimes you need to have a custom watcher
to react to data changes.
For example, you need to check if the user updated his/her name in your app not just triggered a change
event. You can do that by adding a custom watcher for a name
property that will check if the value indeed changed.
var vm = new Vue({
el: '#demo',
data: {
name: '',
nameChanged: false
},
watch: {
name (val, oldVal) {
if (val !== oldVal) this.nameChanged = true
}
}
})
If the name
changed a nameChanged
property will be set to true.