Cannot use <canvas> in framework7-vue

within my framework-vue application, i employed “< canvas >” to draw sth.
but i cannot user canvas.
below is my code snap:

 <canvas class="canvas-wrap">
import {$} from 'dom7'
let ss = $('.canvas-wrap')

console.log(`ss is ${ss}`}
let signaturePad = new SignaturePad(ss);    

print result : ss is [{}]
canvas.getContext is not a function

can anyone tell me how to fix this?

You need to use correct VUE component structure, and not just writing plain JS without anything