/ Miscellaneous

React HoC to handle async loaded fonts

React HoC to handle async loaded fonts

react-with-async-fonts

React module for working with async loaded custom web fonts, based on fontfaceobserver.

Note: version 4.x introduces breaking changes with new API. It addresses bunch of issues, including canceling promises, better performance, and TS typings.

Quick Start

  1. Install react-with-async-fonts:

npm:

npm install --save react-with-async-fonts

yarn:

yarn add react-with-async-fonts
  1. Wrap your root component with FontObserver:

Set prop with font name. You can access it later in FontSubscriber to check if
it's ready.

import { FontObserver } from 'react-with-async-fonts';
import { render } from 'react-dom';
import App from './app';

render(
  <FontObserver openSans="Open Sans">
    <App />
  </FontObserver>,
  document.getElementById('root'),
);
  1. Wrap your target with FontSubscriber component:

Tip: you can also use withFonts API if you're really into
HoCs.

Note that FontSubscriber uses children render prop. Provided function would be
called with single argument which is an object with loaded font keys.

import { FontSubscriber } from 'react-with-async-fonts';

const Heading = ({ children }) => (
  <FontSubscriber>
    {fonts => (
      <h1 className={fonts.openSans ? 'opens-sans-font' : 'system-font'}>
        {children}
      </h1>
    )}
  </FontSubscriber>
);

export default Heading;

API

FontObserver component

import { FontObserver } from 'react-with-async-fonts';
Prop Type Description
text string fontfaceobserver's .load text options
timeout number fontfaceobserver's .load timeout options
[key] Font \| string Font family string or a Font object.

FontSubscriber component

import { FontSubscriber } from 'react-with-async-fonts';
Prop Type Description
children (fonts: Object) => React.Element<any> Children render function. Accepts object with loaded font. Once ready, it would contain object of Font type.

withFonts HoC

import { withFonts } from 'react-with-async-fonts';
Argument Type Description
component React.ComponentType<any> Component to wrap with HoC. Injects fonts object.

Font type

type Font = {
  family: String,
  weight?:
    | 'normal'
    | 'bold'
    | 'bolder'
    | 'lighter'
    | '100'
    | '200'
    | '300'
    | '400'
    | '500'
    | '600'
    | '700'
    | '800'
    | '900',
  style?: 'normal' | 'italic' | 'oblique',
  stretch?:
    | 'normal'
    | 'ultra-condensed'
    | 'extra-condensed'
    | 'condensed'
    | 'semi-condensed'
    | 'semi-expanded'
    | 'expanded'
    | 'extra-expanded'
    | 'ultra-expanded',
};

Examples

Heads up! Each example requires wrapping your app with
FontObserver:

import React from 'react';
import { render } from 'react-dom';
import { FontObserver } from 'react-with-async-fonts';
import App from './app';

render(
  <FontObserver montserrat="Montserrat">
    <App />
  </FontObserver>,
  document.getElementById('root'),
);

Basic with FontSubscriber

import React from 'react';
import { FontSubscriber } from 'react-with-async-fonts';

const Heading = ({ children }) => (
  <FontSubscriber>
    {fonts => (
      <h1 className={fonts.montserrat && 'montserrat-font'}>{children}</h1>
    )}
  </FontSubscriber>
);

export default Heading;

Basic with withFonts

You can use withFonts HoC if you want to compose your component. Please note
it uses same FontSubscriber under the hood.

import React from 'react';
import { withFonts } from 'react-with-async-fonts';

const Heading = ({ children, fonts }) => (
  <h1 className={fonts.montserrat && 'montserrat-font'}>{children}</h1>
);

export default withFonts(Heading);

With styled-components

Most elegant way of using it with styled-components is withFonts HoC.

import styled from 'styled-components';
import { withFonts } from 'react-with-async-fonts';

const Heading = styled.h2`
  font-weight: 300;
  font-family: ${props =>
    props.fonts.montserrat
      ? '"Open Sans", sans-serif'
      : 'Helvetica, sans-serif'};
`;

export default withFonts(Heading);

Nested FontObserver

You can nest FontObserver to merge fonts. Children instances overrides parent
if font with same code was defined.

import { FontObserver, FontSubscriber } from 'react-with-async-fonts';

const Article = ({ title, children }) => (
  <FontObserver roboto="Roboto">
    <FontObserver ptSans="PT Sans">
      <FontSubscriber>
        {fonts => (
          <article>
            <h1 className={fonts.roboto ? 'roboto' : 'sans-serif'}>{title}</h1>
            <p className={fonts.ptSans ? 'ptsans' : 'serif'}>{children}</p>
          </article>
        )}
      </FontSubscriber>
    </FontObserver>
  </FontObserver>
);

export default Article;

Custom fontfaceobserver options

You can provide text and timeout options for
fontfaceobserver's .load
method with same props.

import { FontObserver, FontSubscriber } from 'react-with-async-fonts';

const Heading = ({ children }) => (
  <FontObserver text={children} timeout={2500} roboto="Roboto">
    <FontSubscriber>
      {fonts => <h1 className={fonts.roboto && 'roboto'}>{children}</h1>}
    </FontSubscriber>
  </FontObserver>
);

export default Heading;

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