title: Merge mixin in vue
body: <p>I'm working in vue/quasar application.
  I've my mixin like this in my view.cshtml</p>
  <pre><code>var mixin1 = {
          data: function () {
              return { data1:0,data2:'' }
          }
          ,
          beforeCreate: async function () {
              ...}
          },
          methods: {
              addformulaire(url) {
                 
              },
              Kilometrique() {  }
            
          }
      }
  </code></pre>
  <p>And I want merge with my content in js file (it's to centralize same action an severals cshtml)</p>
  <pre><code>const nomeMixins = {
  data: function () {
      return { loadingcdt: false, lstclt: [], filterclient: [], loadingdoc: false, lstdoc: [], filterdoc: [] }
  },
  computed: {
      libmntpiece(v) { return &quot;toto&quot;; }
  },
  methods: {
      
      findinfcomplemtX3(cdecltx3, cdedocx3) {
          
      },
      preremplissagex3: async function (cdecltx3, cdedocx3) {
         
          }
      }
  }
  </code></pre>
  <p>};</p>
  <p>I want merge this 2 miwin in one. But when I try assign or var mixin = { ...mixin1,  ...nomeMixins };
  I've only mixin1 nothing about methods,data from my js file nomeMixins but merging failed cause I've same key in my json object. I'm trying to make a foreach but failed too</p>
  <p>Someone try to merge to mixin / json object with same key in the case you've no double child property ?</p>