js清空数组

vue.js

 var map={
     message: '',
     placeMb :[],
     cc:'',
};

new Vue({
    el: '#app',
    data: map
})


$("#cancel).click(function(){
     $.get("/applyinfo/getApplyinfoCard",{},function(data){
         map.placeMb = data.placeMb,
    });
})

怎么清空map里面定义的placeMb 数组
详细：
http://yayihouse.com/yayishuwu/chapter/1979