TS2345：“HTMLElement”类型的参数不可分配给“ChartItem”类型的参数

Question

I'm working on an Angular dashboard development and I found this error that doesn't let me render area chart

import { AfterViewInit, Component, ElementRef, Input, OnInit, ViewChild } from '@angular/core';
import { Chart } from 'chart.js';

@Component({
selector: 'app-widget-area',
templateUrl: './area.component.html',
styleUrls: ['./area.component.scss']
})
export class AreaComponent implements AfterViewInit {


 constructor() {}
 ngAfterViewInit() {
    let elem: HTMLElement;
    const ctx = document.getElementById("myChart") as HTMLElement;
     if (ctx) {
        elem = ctx;
        const myChart = new Chart(elem, {
            data: {
                datasets: [
                    { fill: 'origin' },      // 0: fill to 'origin'
                    { fill: '+2' },         // 1: fill to dataset 3
                    { fill: 1 },             // 2: fill to dataset 1
                    { fill: false },         // 3: no fill
                    { fill: '-2' },          // 4: fill to dataset 2
                    { fill: { value: 25 } }    // 5: fill to axis value 25
                ]
            }
        });
    }
}

And got this error:

TS2345: Argument of type 'HTMLElement' is not assignable to parameter of type 'ChartItem'.
Type 'HTMLElement' is missing the following properties from type 'HTMLCanvasElement': height, width, captureStream, getContext, and 2 more.

I've tried with all the internet stuff and nothing worked for me, anyone have the same error? BTW this is my simply html, I have my NgChartModule from charjs and nothing worked for me

<div>
  <div style="display: block">
  <canvas id="myChart " ></canvas>

  </div>
</div>

Answer 1

Chart class' constructor take the first parameter ( item ) as ChartItem type where ChartItem takes type of:

ChartItem: string | CanvasRenderingContext2D | HTMLCanvasElement | { canvas: HTMLCanvasElement } | ArrayLike<CanvasRenderingContext2D | HTMLCanvasElement>

From here , you can see the usage:

const ctx = document.getElementById('myChart');
const ctx = document.getElementById('myChart').getContext('2d');
const ctx = $('#myChart');
const ctx = 'myChart';

const ctx = document.getElementById("myChart");
if (ctx) {
    const myChart = new Chart(ctx, {
            data: {
                datasets: [
                    { fill: 'origin' },      // 0: fill to 'origin'
                    { fill: '+2' },         // 1: fill to dataset 3
                    { fill: 1 },             // 2: fill to dataset 1
                    { fill: false },         // 3: no fill
                    { fill: '-2' },          // 4: fill to dataset 2
                    { fill: { value: 25 } }    // 5: fill to axis value 25
                ]
            }
        });
}