How to return string from a Promise

Question

Im working on a website with vue where i have to get images with axios from a server and put them as background images of divs. The case is that i have the urls but not all of them are correct. So im trying to make a function that makes an http request and returns me the url if that request is successful.

I thought of something like this:

Template:

<div class="element" :style="bgImg(url)"/>

Script:

methods: {
  bgImg(url) {
    axios.get(url)
      .then(response => {
        return `background-image: url(${response.config.url})`;
      })
      .cath(e) {
        throw new Error(e);
      }
  }
}

I was expecting to get the url returned from that function, but nothing happens.

Answer 1

You could use a custom vue directive for that job:

Vue.directive('validate-bgimg', function (el, binding) {  
  el.style.backgroundImage = null  // reset 
  var url = binding.value
  if (!url) {
    return
  }
  axios.get(`https://cors-anywhere.herokuapp.com/${url}`)  // get around CORS limitations. Idealy you should call your own api to validate image urls
  .then(response => {
    if (response.status != 200) {
      console.warn("Invalide image url", url, response)
    } else {
      el.style.backgroundImage = `url(${url})`
    }
  })
  .catch(e => {
    console.error("Could not validate image", url, e)
  })
})


new Vue({
  el: "#app",
  data: {
    imgUrl: undefined
  }
})

#app {
  background: lightgray;
  border-radius: 4px;
  padding: 20px;
  margin: 20px;
  transition: all 0.2s;
}

.element {
  margin: 8px 0;
  width: 200px;
  height: 200px;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/axios/0.18.0/axios.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.17/vue.js"></script>

<div id="app">
  <b>test case:</b>
  <button @click="imgUrl='https://dummyimage.com/200x200/000/fff.gif&text=test+1'">1</button>
  <button @click="imgUrl='https://dummyimage.com/200x200/000/fff.gif&text=test+2'">2</button>
  <button @click="imgUrl='https://dummyimage.com/200x200/000/fff.gif&text=test+3'">3</button>
  <button @click="imgUrl='https://httpbin.org/status/404'">HTTP 404</button>
  <button @click="imgUrl='https://httpbin.org/status/503'">HTTP 503</button>
  <button @click="imgUrl='https://invalid.tld'">cannot resolve domain name</button>
  
  <div class="element" v-validate-bgimg="imgUrl"/>
</div>