Global function to convert minutes to hours in vue-cli - vuejs2

Question

I want to convert time (in minutes) to hours.
I have a method for that in javascript:
String.prototype.toHHMMSS = function() {
// eslint-disable-next-line no-debugger
return `0${(this / 60) ^ 0}`.slice(-2) + ":" + ("0" + (this % 60)).slice(-2);
};
While I am using this method outside the vue instances, this method works well like in the example shown below.
String.prototype.toHHMMSS = function() {
// eslint-disable-next-line no-debugger
return `0${(this / 60) ^ 0}`.slice(-2) + ":" + ("0" + (this % 60)).slice(-2);
};
var vm = new Vue({
el: '#app',
methods: {
html() {
return `<span> <strong><i>${this.time.toHHMMSS()}</i></strong> Spent in Week 2</span>`
}
},
data() {
return {
time: "121",
}
}
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.17/vue.js"></script>
<div id="app">
<div v-html="html()" />
</div>
But I am using the vue-cli, and want to use that method in the data. similar to the shown in the example.
But it's not working, while I used that before export default {} in the component or, I used as:
export default {
install(Vue, options) {
Vue.prototype.toHHMMSS = function (object) {
return false // dummy function for now to check if method works
}
}
}
I know of using the mixins for a similar purpose, but is there a way to make this work without the mixin?

Answer 1

Puts the following code in a file named helper.js or whatever you want
export function toHHMMSS(time) {
return `0${(this / 60) ^ 0}`.slice(-2) + ":" + ("0" + (this % 60)).slice(-2);
};
Then in your vue file, use import below the tag of <script>
import * as Helper from "helper.js" // Note the file location
Now you can use the following code in your function
var formatedTime = Helper.toHHMMSS(this.time)