比如myfunction.js文件

module.exports={
    /*
     * 单一数组转根据ID和PID转日录树
     * 用法，listToTree(array,{
     *  "idKey":"id",//id
     *  "parentKey":"parent",//父ID
     *  "children":"children"//子ID名
     * });
     * @date 数据组
     * @options 格式化方法 传入 ID PID 和子目录名
     */
    //listToTree:function (data, options) {
    listToTree:function (data, {idKey='id',parentKey="pid",childrenKey='children'}={}) {
        /*options = options || {};
        let ID_KEY = options.idKey || 'id';
        let PARENT_KEY = options.parentKey || 'pid';
        let CHILDREN_KEY = options.childrenKey || 'children';*/

        let tree = [],childrenOf = {},length = data.length;
        let item,id,parentId;

        for (let i = 0; i < length; i++) {
            item = data[i];
            id = item[idKey];
            parentId = item[parentKey] || 0;
            // every item may have children
            childrenOf[id] = childrenOf[id] || [];
            // init its children
            item[childrenKey] = childrenOf[id];
            if (parentId != 0) {
            // init its parent's children object
            childrenOf[parentId] = childrenOf[parentId] || [];
            // push it into its parent's children object
            childrenOf[parentId].push(item);
            } else {
                tree.push(item);
            }
        }

    return tree;
    } 
        //可以写多个方法或是自己定义变量。
}

再到main.js里面注册

import myfunctionfrom './components/common/myfunction.js'
Vue.prototype.$comFun = myfunction

在组件里直接调用

this.$comFun.listToTree(data);

这样就可以把自已经常会用的函数和值存在里面调用。但一定要保证调用时this指向的是VUE。