Vue复选框checkbox全选与取消全选

new Vue({
el: '#app',
data: {
checked: false,
checkedNames: [],
checkedArr: ["Runoob", "Taobao", "Google"]
},
methods: {
changeAllChecked: function() {
if (this.checked) {
this.checkedNames = this.checkedArr
} else {
this.checkedNames = []
}
}
},
watch: {
"checkedNames": function() {
if (this.checkedNames.length == this.checkedArr.length) {
this.checked = true
} else {
this.checked = false
}
}
}
})