onload vue

vm=new Vue({
  el:"#app",
  mounted:function(){
        this.method1() //method1 will execute at pageload
  },
  methods:{
        method1:function(){
              /* your logic */
        }
     },
})methods: {
     getUnits: function() {...}
 },
 beforeMount() {
    this.getUnits()
 }

________________________________________________________________________________

beforeCreate: Called synchronously after the instance has just been initialized,
before data observation and event/watcher setup.

created: Called synchronously after the instance is created. At this stage,
the instance has finished processing the options which means the following have been set up: data observation, computed properties, methods, watch/event callbacks. However, the mounting phase has not been started, and the $el property will not be available yet.

beforeMount: Called right before the mounting begins: the render function is
about to be called for the first time.

mounted: Called after the instance has just been mounted where el is replaced
by the newly created vm.$el.

beforeUpdate: Called when the data changes, before the virtual DOM is
re-rendered and patched.

updated: Called after a data change causes the virtual DOM to be re-rendered
and patched.

You can have a look at complete list here:
https://vuejs.org/v2/api/#Options-Lifecycle-Hooks