title: Pushing to array causes error in Vuejs when attempting to add data
body: <p>I am working on an infinite scroll solution and I am trying to push data onto an array of objects, but I am getting an error:</p>
  
  <pre><code>vue.common.js?e881:2643 [Vue warn]: Error when rendering anonymous component at /Users/Deric/Sites/mobile/lawn-mobile/src/components/jobs/index.vue: warn @ vue.common.js?e881:2643Vue._render @ vue.common.js?e881:2253(anonymous function) @ vue.common.js?e881:1699get @ vue.common.js?e881:736run @ vue.common.js?e881:805flushSchedulerQueue @ vue.common.js?e881:623nextTickHandler @ vue.common.js?e881:401
  vue.common.js?e881:2262 TypeError: Cannot read property 'length' of undefined(…)
  </code></pre>
  
  <p>If i just set the data, it works, but the infinite scroll overwrites the data instead of appending to it. Here is my data object:</p>
  
  <pre><code>data () {
    return {
      jobs: [],
  </code></pre>
  
  <p>and here is my http call:</p>
  
  <pre><code>getJobs(pageNumber = 1) {
    let api = SessionStorage.get.item('api')
    let url = `${api.base_url}jobs?page=${pageNumber}`
    this.$http.get(url).then((response) =&gt; {
      console.log(response.body.data)
      this.jobs.push(response.body.data)
  </code></pre>
  
  <p>The <code>console.log</code> looks like this:</p>
  
  <p><a href="https://i.stack.imgur.com/S2sIE.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/S2sIE.png" alt="enter image description here"></a></p>
  
  <p>What is the trick to getting this to work? I have also tried <code>concat</code> but that doesn't work either.</p>