v-bind:src not working?

Question

Vue.js

Hello, there was such a problem, there is img :bind="func()", in the function if, else check, in each return that displays the desired value, when the page is loaded, the value from the if is set, then else works (checked through the console), but the value in :src doesn't change, why?
img: Function:
<img :src="onValue()">

onValue(val) {
      if(val === undefined) {
        console.log('aaa',val)
        return require('@/assets/img/lazer1.gif');
      }
      else if(val >= 0){
        console.log(val) //выводит val (1,2,3,4,5)
        return require('@/assets/img/lazer'+ val +'.gif'); //это значение не возращается
      }
    }

Thanks in advance!