How could I change the value of this.buttonState in this scenary? - vue.js

Question

I'm having issues in this process . First is that I have a button in disabled state(true) and I need to change that value to false when the video is uploaded . I have this scenary and I think I got a windows object inside the changing method . Any idea, help please . I'm getting undefined value for the variable.
data: () => ({
buttonState: true} }),
changeBehavior() {
let self
(function () {
const input = document.getElementById('uploader')
self = this
console.log(this)
const changing = ({ target: { files } }) => {
if (input.files.length > 0) {
// self.buttonState = false
const video = document.getElementById('output-video')
video.src = URL.createObjectURL(files[0])
}
}
input.addEventListener('change', changing)
})()
const au = document.getElementById('output-video')
au.onloadedmetadata = () => {
const hidden = document.getElementById('hiddenSlider')
hidden.removeAttribute('hidden')
const muteHidden = document.getElementById('muteHidden')
muteHidden.removeAttribute('hidden')
self = this
self.range = [0, au.duration]
this.max = au.duration
const secNum = parseInt(au.duration, 10)
let hours = Math.floor(secNum / 3600)
let minutes = Math.floor((secNum - (hours * 3600)) / 60)
let seconds = secNum - (hours * 3600) - (minutes * 60)
if (hours < 10) {
hours = '0' + hours
}
if (minutes < 10) {
minutes = '0' + minutes
}
if (seconds < 10) {
seconds = '0' + seconds
}
document.getElementById('renderizado').innerHTML =
hours + ':' + minutes + ':' + seconds
}
},
<v-btn
id="run"
class="accent-3 blue ml-15"
dark
#click="$refs.inputUpload.click()"
>
<input
v-show="false"
id="uploader"
ref="inputUpload"
accept=".mkv,video/*"
type="file"
#click="changeBehavior"
>
Select to Upload Video
</v-btn>
<v-btn
id="doTrimming"
block
class="accent-3 blue mt-5"
dark
:disabled="buttonState"
#click="cutIt"
>
Trim Video Now
</v-btn>

Answer 1

Where you define self you need to assign this to it then.
changeBehavior() {
const self = this;
const callback = function() {
// now you can access the vue instance when in another functions scope
self.buttonState = true;
}
}