How to check if a div is overflowing in react functional component

Question

I am trying to find out if a div has overflown text and show show more link if it does. I found this stackoverflow answer to check if a div is overflowing. According to this answer, I need to implement a function which can access styles of the element in question and do some checks to see if it is overflowing. How can I access the styles of an element. I tried 2 ways

1. Using ref

import React from "react";
import "./styles.css";

export default function App(props) {
  const [showMore, setShowMore] = React.useState(false);
  const onClick = () => {
    setShowMore(!showMore);
  };

  const checkOverflow = () => {
    const el = ref.current;
    const curOverflow = el.style.overflow;

    if ( !curOverflow || curOverflow === "visible" )
        el.style.overflow = "hidden";

    const isOverflowing = el.clientWidth < el.scrollWidth 
        || el.clientHeight < el.scrollHeight;

    el.style.overflow = curOverflow;

    return isOverflowing;
  };

  const ref = React.createRef();

  return (
    <>
      <div ref={ref} className={showMore ? "container-nowrap" : "container"}>
        {props.text}
      </div>
      {(checkOverflow()) && <span className="link" onClick={onClick}>
        {showMore ? "show less" : "show more"}
      </span>}
    </>
  )
}

2. Using forward ref

Child component

export const App = React.forwardRef((props, ref) => {
  const [showMore, setShowMore] = React.useState(false);
  const onClick = () => {
    setShowMore(!showMore);
  };

  const checkOverflow = () => {
    const el = ref.current;
    const curOverflow = el.style.overflow;

    if (!curOverflow || curOverflow === "visible") el.style.overflow = "hidden";

    const isOverflowing =
      el.clientWidth < el.scrollWidth || el.clientHeight < el.scrollHeight;

    el.style.overflow = curOverflow;

    return isOverflowing;
  };

  return (
    <>
      <div ref={ref} className={showMore ? "container-nowrap" : "container"}>
        {props.text}
      </div>
      {checkOverflow() && (
        <span className="link" onClick={onClick}>
          {showMore ? "show less" : "show more"}
        </span>
      )}
    </>
  );
});

Parent component

import React from "react";
import ReactDOM from "react-dom";

import { App } from "./App";

const rootElement = document.getElementById("root");
const ref = React.createRef();
ReactDOM.render(
  <React.StrictMode>
    <App
      ref={ref}
      text="Start editing to see some magic happen! Click show more to expand and show less to collapse the text"
    />
  </React.StrictMode>,
  rootElement
);

But I got the following error in both approaches - Cannot read property 'style' of null. What am I doing wrong? How can I achieve what I want?

Answer 1

As Jamie Dixon suggested in the comment, I used useLayoutEffect hook to set showLink true. Here is the code

Component

import React from "react";
import "./styles.css";

export default function App(props) {
  const ref = React.createRef();
  const [showMore, setShowMore] = React.useState(false);
  const [showLink, setShowLink] = React.useState(false);

  React.useLayoutEffect(() => {
    if (ref.current.clientWidth < ref.current.scrollWidth) {
      setShowLink(true);
    }
  }, [ref]);

  const onClickMore = () => {
    setShowMore(!showMore);
  };

  return (
    <div>
      <div ref={ref} className={showMore ? "" : "container"}>
        {props.text}
      </div>
      {showLink && (
        <span className="link more" onClick={onClickMore}>
          {showMore ? "show less" : "show more"}
        </span>
      )}
    </div>
  );
}

CSS

.container {
  overflow-x: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
  width: 200px;
}

.link {
  text-decoration: underline;
  cursor: pointer;
  color: #0d6aa8;
}