use-fit-text

React hook that iteratively adjusts the font size so that text will fit in a div.

• checks if text is overflowing by using scrollHeight and offsetHeight
• recalculates when container is resized (using (polyfilled) ResizeObserver)
• recalculates when content changes
• uses binary search; with default options, makes a maximum of 5 adjustments with a resolution of 5% font size from 20-100%
• < 4 kB minified + gzipped
• written in TypeScript

Installation

npm install --save use-fit-text

Usage

import React from "react";
import useFitText from "use-fit-text";

function Example() {
  const { fontSize, ref } = useFitText();

  return (
    <div ref={ref} style={{ fontSize, height: 40, width: 100 }}>
      Lorem ipsum dolor sit amet, consectetur adipiscing elit.
    </div>
  );
}

Demo / example code

• Demo site: https://saltycrane.github.io/use-fit-text/
• Example code is in the /examples folder

API

useFitText(options)

• Returns an object with the following properties:

  • fontSize (string) - the font size as a string (CSS percent) to be passed as the fontSize property of the style prop of the div
  • ref (React.MutableRefObject<HTMLDivElement>) - the ref to be passed to the ref attribute of the div

• options (optional) - an object with the following optional properties:

  • logLevel (string, default: info) - one of debug, info, warn, error, or none
  • maxFontSize (number, default: 100) - maximum font size in percent
  • minFontSize (number, default: 20) - minimum font size in percent
  • onFinish ((fontSize: number) => void, default: undefined) - function that is called when resizing finishes. The final fontSize is passed to the function as an argument.
  • onStart (() => void, default: undefined) - function that is called when resizing starts
  • resolution (number, default: 5) - font size resolution to adjust to in percent

Questions

• Why doesn't it work with Flexbox justify-content: flex-end;? This appears to be a bug with Flexbox. Try using CSS Grid or margin-top: auto;
• What does the "reached minFontSize = 20 without fitting text" message in the console mean? This means use-fit-text was not able to fit the text using the minFontSize setting of 20. To ensure the text fits, set minFontSize to a smaller value.

Changelog

• v2.4.0
  • handle case where minFontSize is set larger than the fontSize value needed to fit the text in the div. Log a message to the console in this case.
  • fix final adjustment calcuation
  • add logLevel option to control what is logged to the console
• v2.3.0
  • automatically recalculate font size when content changes
  • fix bug where a recalculation was not done on resize if the text initially fit in the div
• v2.2.0 - add onStart and onFinish callbacks
• v2.1.3 - export TOptions TypeScript type
• v2.1.2 - remove /// <reference types="next" /> in dist/index.d.ts
• v2.1.0
  • fix SSR/prerender issue where text did not resize
  • suppress useLayoutEffect warning for server render
• v2.0.0
  • use ResizeObserver to always recalculate on container resize
  • remove recalcOnResize option
  • useLayoutEffect instead of useEffect to avoid flashing
• v1.2.1 - fix scrollbar issue in example
• v1.2.0 - add recalcOnResize and other options
• v1.1.0 - fix binary search bug
• v1.0.2 - add example
• v1.0.0 - initial release