我正在尝试使用 getElementsByClassName 来 select 一个 canvas 元素，但我能得到的只是一个元素数组

Question

(working in ReactJS)

I am trying to get the correct canvas dom element but I am only able to get an array of elements and I can't seem to use standard array syntax to return the specific element I want to work on.

import React, {Component} from "react";
import "./Mountaincanvas.scss"

const MountainCanvas = () => {
    const canvas = document.getElementsByClassName("mountain-canvas");
    console.log(canvas)
    console.log(canvas[0])
    return (
        <canvas className="mountain-canvas"/>
        )
    }

export default MountainCanvas;

The first time I console log the canvas variable I get a HTMLCollection with a single element

HTMLCollection[]
>0: canvas.mountain-canvas
 length: 1
 __proto__:HTMLCollection

however if I try to just get the first element of the array I get undefined. How do I select just the first element of the array so I can do things like get Context? or simple styling?

Answer 1

If you're trying to get a handle to the canvas in the current component, use a ref :

const MountainCanvas = () => {
  const canvas = React.useRef();
  
  if (canvas.current) {
    // do stuff with the canvas
  }

  return (
    <canvas ref={canvas} className="mountain-canvas"/>
  )
}