TypeError: Cannot read property 'width' of undefined - Nuxt JS and canvas - vue.js

Question

I am trying to run a sketch on the canvas element in Nuxt JS but I am having some issues (I am completely new to Vue JS).
While I have no errors in VS Code, there is an error in the browser console:
client.js?06a0:84 TypeError: Cannot read property 'width' of undefined
at Blob.get (Blob_Point.js?a5e5:126)
at Blob.render (Blob_Point.js?a5e5:29)
below is the code for my Vue file:
<template>
<div>
<h1 class="pa-5 text-center">Blob</h1>
<canvas id="myCanvas" width="600" height="400"></canvas>
<!--<v-btn #click="drawRect">Clear</v-btn> -->
</div>
</template>
<script>
import Blob from "../assets/content/Blob_Point"
//import { Point } from "../assets/content/Blob_Point"
//import Point from "../assets/content/Blob_Point"
let oldMousePoint = { x: 0, y: 0 }
let blob = new Blob()
//let point = new Point()
let hover = false
let canvas
export default {
data() {
return {
canvas: null,
x: 0,
y: 0,
isDrawing: false,
rectWidth: 200,
//hover: false,
//oldMousePoint: { x: 0, y: 0 },
}
},
mounted() {
let canvas = document.getElementById("myCanvas")
this.canvas = canvas.getContext("2d")
},
created() {
new Blob("#C09EFF")
blob.canvas = canvas
blob.init()
blob.render()
},
methods: {
/* showCoordinates(e) {
this.x = e.offsetX
this.y = e.offsetY
},
drawLine(x1, y1, x2, y2) {
let ctx = this.vueCanvas
ctx.beginPath()
ctx.strokeStyle = "black"
ctx.lineWidth = 1
ctx.moveTo(x1, y1)
ctx.lineTo(x2, y2)
ctx.stroke()
ctx.closePath()
},
draw(e) {
if (this.isDrawing) {
this.drawLine(this.x, this.y, e.offsetX, e.offsetY)
this.x = e.offsetX
this.y = e.offsetY
}
},
beginDrawing(e) {
this.x = e.offsetX
this.y = e.offsetY
this.isDrawing = true
},
stopDrawing(e) {
if (this.isDrawing) {
this.drawLine(this.x, this.y, e.offsetX, e.offsetY)
this.x = 0
this.y = 0
this.isDrawing = false
//windowWidth = 0,
}
}, */
resize() {
document.getElementById("myCanvas").width = window.innerWidth
document.getElementById("myCanvas").height = window.innerHeight
},
/*drawRect() {
this.vueCanvas.clearRect(0, 0, 600, 800)
//this.vueCanvas.beginPath()
//this.vueCanvas.rect(20, 20, this.rectWidth, 100)
//this.vueCanvas.stroke()
},*/
mouseMove(e) {
let pos = blob.center
let diff = { x: e.clientX - pos.x, y: e.clientY - pos.y }
let dist = Math.sqrt(diff.x * diff.x + diff.y * diff.y)
let angle = null
blob.mousePos = {
x: pos.x - e.clientX,
y: pos.y - e.clientY,
}
if (dist < blob.radius && hover === false) {
let vector = {
x: e.clientX - pos.x,
y: e.clientY - pos.y,
}
angle = Math.atan2(vector.y, vector.x)
hover = true
// blob.color = '#77FF00';
} else if (dist > blob.radius && hover === true) {
let vector = {
x: e.clientX - pos.x,
y: e.clientY - pos.y,
}
angle = Math.atan2(vector.y, vector.x)
hover = false
blob.color = null
}
if (typeof angle == "number") {
let nearestPoint = null
let distanceFromPoint = 100
blob.points.forEach((point) => {
if (Math.abs(angle - point.azimuth) < distanceFromPoint) {
// console.log(point.azimuth, angle, distanceFromPoint);
nearestPoint = point
distanceFromPoint = Math.abs(angle - point.azimuth)
}
})
if (nearestPoint) {
let strength = {
x: oldMousePoint.x - e.clientX,
y: oldMousePoint.y - e.clientY,
}
strength =
Math.sqrt(strength.x * strength.x + strength.y * strength.y) * 1
if (strength > 100) strength = 100
nearestPoint.acceleration = (strength / 100) * (hover ? -1 : 1)
}
}
oldMousePoint.x = e.clientX
oldMousePoint.y = e.clientY
},
},
}
</script>
<style scoped>
#myCanvas {
border: 1px solid grey;
}
</style>
and below is the Blob_Point JS file that I am importing:
/* eslint-disable */
// Blob Class
export default class Blob {
// setup function
constructor(color) {
//the objects setup
// 'this' is a reference to the current class
this.points = []
this._color = color
}
init() {
for (let i = 0; i < this.numPoints; i++) {
let point = new Point(this.divisional * (i + 1), this)
//point.acceleration = -1 + Math.random() * 2;
this.push(point)
}
}
render() {
let canvas = this.canvas
let ctx = this.ctx
let position = this.position
let pointsArray = this.points
let radius = this.radius
let points = this.numPoints
let divisional = this.divisional
let center = this.center
ctx.clearRect(0, 0, canvas.width, canvas.height)
pointsArray[0].solveWith(pointsArray[points - 1], pointsArray[1])
let p0 = pointsArray[points - 1].position
let p1 = pointsArray[0].position
let _p2 = p1
// this is the draw
ctx.beginPath()
ctx.moveTo(center.x, center.y)
ctx.moveTo((p0.x + p1.x) / 2, (p0.y + p1.y) / 2)
for (let i = 1; i < points; i++) {
pointsArray[i].solveWith(
pointsArray[i - 1],
pointsArray[i + 1] || pointsArray[0]
)
let p2 = pointsArray[i].position
var xc = (p1.x + p2.x) / 2
var yc = (p1.y + p2.y) / 2
ctx.quadraticCurveTo(p1.x, p1.y, xc, yc)
// ctx.lineTo(p2.x, p2.y);
//ctx.fillStyle = this.color;
// ctx.fillRect(p1.x-2.5, p1.y-2.5, 5, 5);
p1 = p2
}
var xc = (p1.x + _p2.x) / 2
var yc = (p1.y + _p2.y) / 2
ctx.quadraticCurveTo(p1.x, p1.y, xc, yc)
ctx.lineTo(_p2.x, _p2.y)
ctx.closePath()
ctx.fillStyle = this.color
ctx.fill()
ctx.strokeStyle = this.color
// ctx.stroke();
/*
ctx.fillStyle = '#000000';
if(this.mousePos) {
let angle = Math.atan2(this.mousePos.y, this.mousePos.x) + Math.PI;
}*/
//requestAnimationFrame(this.render.bind(this))
}
push(item) {
if (item instanceof Point) {
this.points.push(item)
}
}
set color(value) {
this._color = value
}
get color() {
return this._color
}
set canvas(value) {
if (
value instanceof HTMLElement &&
value.tagName.toLowerCase() === "canvas"
) {
this._canvas = canvas
this.ctx = this._canvas.getContext("2d")
}
}
get canvas() {
return this._canvas
}
set numPoints(value) {
if (value > 10) {
this._points = value
}
}
get numPoints() {
return this._points || 32
}
set radius(value) {
if (value > 0) {
this._radius = value
}
}
get radius() {
return this._radius || 300
}
set position(value) {
if (typeof value == "object" && value.x && value.y) {
this._position = value
}
}
get position() {
return this._position || { x: 0.5, y: 0.5 }
}
get divisional() {
return (Math.PI * 2) / this.numPoints
}
get center() {
return {
x: this.canvas.width * this.position.x,
y: this.canvas.height * this.position.y,
}
}
set running(value) {
this._running = value === true
}
get running() {
return this.running !== false
}
}
// Point Class
export class Point {
constructor(azimuth, parent) {
this.parent = parent
this.azimuth = Math.PI - azimuth
this._components = {
x: Math.cos(this.azimuth),
y: Math.sin(this.azimuth),
}
this.acceleration = -0.3 + Math.random() * 0.6
}
solveWith(leftPoint, rightPoint) {
this.acceleration =
(-0.3 * this.radialEffect +
(leftPoint.radialEffect - this.radialEffect) +
(rightPoint.radialEffect - this.radialEffect)) *
this.elasticity -
this.speed * this.friction
}
set acceleration(value) {
if (typeof value == "number") {
this._acceleration = value
this.speed += this._acceleration * 2
}
}
get acceleration() {
return this._acceleration || 0
}
set speed(value) {
if (typeof value == "number") {
this._speed = value
this.radialEffect += this._speed * 3
}
}
get speed() {
return this._speed || 0
}
set radialEffect(value) {
if (typeof value == "number") {
this._radialEffect = value
}
}
get radialEffect() {
return this._radialEffect || 0
}
get position() {
return {
x:
this.parent.center.x +
this.components.x * (this.parent.radius + this.radialEffect),
y:
this.parent.center.y +
this.components.y * (this.parent.radius + this.radialEffect),
}
}
get components() {
return this._components
}
set elasticity(value) {
if (typeof value === "number") {
this._elasticity = value
}
}
get elasticity() {
return this._elasticity || 0.001
}
set friction(value) {
if (typeof value === "number") {
this._friction = value
}
}
get friction() {
return this._friction || 0.0085
}
}
Any ideas on the why lines 29 and 127 of the Blob_Point.js file are throwing errors?
I attached 2 screens of the developer tools in chrome to show the errors along with the JS its pointing to.
Thanks for any help!

Answer 1

The main issue I can identify is here. I have added comments to the code.
Blob_Point.js
render() {
let canvas = this.canvas // this references the Blob Class (not the Vue instance) and there is no initialised property such as canvas in the class
}
To fix this main issue, you can do something like
Blob_Point.js
export default class Blob {
constructor(color, canvas) {
//the objects setup
// 'this' is a reference to the current class
this.points = []
this._color = color;
this.canvas = canvas
}
}
And then in the .vue file
.Vue
mounted() {
let canvas = document.getElementById("myCanvas");
this.canvas = canvas.getContext("2d");
blob = new Blob("#C09EFF", this.canvas); // now canvas in the Blob Class constructor will refer to the vue instance canvas
blob.canvas = canvas;
blob.init();
blob.render();
},
I have identified another issue here.
set canvas(value) {
if (
value instanceof HTMLElement &&
value.tagName.toLowerCase() === "canvas"
) {
this._canvas = canvas // there is no initialised constructor property as _canvas
this.ctx = this._canvas.getContext("2d") // there is no initialised constructor property such as _canvas
}
}
get canvas() {
return this._canvas // there is no initialised constructor property as _canvas
}