react-katex

Display math with KaTeX and ReactJS!

Installing

You can install it with npm:

  $ npm install --save react-katex

With Yarn:

  $ yarn add react-katex

Or use one of the files inside the dist folder.

When using react-katex directly from the browser, react-katex will export a global called ReactKaTeX. Notice that the T and X from "KaTeX" are uppercased.

Don't forget to import KaTeX CSS file (see example/index.html).

If you open the example file on Firefox directly (i.e. without a server) the fonts won't load, open it on Chrome or put it on some server. You can use some static one-liner.

Usage

react-katex has two types of math components, InlineMath and BlockMath.

InlineMath

Display math in the middle of the text.

  var InlineMath = ReactKaTeX.InlineMath;

  ReactDOM.render(<InlineMath math="\\int_0^\\infty x^2 dx"/>,
                document.getElementById('math'));

  // or

  ReactDOM.render(<InlineMath>\int_0^\infty x^2 dx</InlineMath>,
                document.getElementById('math'));

It will be rendered like this:

BlockMath

Display math in a separated block, with larger font and symbols.

  var BlockMath = ReactKaTeX.BlockMath;

  ReactDOM.render(<BlockMath math="\\int_0^\\infty x^2 dx"/>,
                document.getElementById('math'));

  // or

  ReactDOM.render(<BlockMath>\int_0^\infty x^2 dx</BlockMath>,
                document.getElementById('math'));

It will be rendered like this:

Error handling

Default error message

By default the error rendering is handled by KaTeX. You can optionally pass errorColor (defaults to #cc0000) as a prop:

var BlockMath = ReactKaTeX.BlockMath;

ReactDOM.render(
  <BlockMath
    math={'\\int_0^\\infty x^2 dx \\inta'}
    errorColor={'#cc0000'}
  />, document.getElementById('math'));

This will be rendered like so:

Custom error message

It's possible to handle parse errors using the prop renderError. This prop must be a function that receives the error object and returns what should be rendered when parsing fails:

var BlockMath = ReactKaTeX.BlockMath;

ReactDOM.render(
  <BlockMath
    math="\\int_{"
    renderError={(error) => {
      return <b>Fail: {error.name}</b>
    }}
  />,
  document.getElementById('math'));

// The code above will render '<b>Fail: ParseError</b>' because it's the value returned from `renderError`.

This will render <b>Fail: ParseError</b>:

Escaping expressions

In addition to using the math property, you can also quote as a child allowing the use of { } in your expression.

ReactDOM.render(<BlockMath>{"\\frac{\\text{m}}{\\text{s}^2}"}</BlockMath>,
                document.getElementById('math'));

Or Multiline

ReactDOM.render(<BlockMath>{`\\frac{\\text{m}}
{\\text{s}^2}`}</BlockMath>,
                document.getElementById('math'));

However, it can be annoying to escape backslashes. This can be circumvented with the String.raw tag on a template literal when using ES6.

ReactDOM.render(<BlockMath>{String.raw`\frac{\text{m}}{\text{s}^2}`}</BlockMath>,
                document.getElementById('math'));

Backticks must be escaped with a backslash but would be passed to KaTeX as \`. A tag can be created to replace \` with `

const latex = (...a) => String.raw(...a).replace("\\`","`")
ReactDOM.render(<BlockMath>{latex`\``}</BlockMath>,
                document.getElementById('math'));

You can even do variable substitution

const top = "m";
const bottom = "s";
ReactDOM.render(<BlockMath>{String.raw`\frac{\text{${top}}}{\text{${bottom}}^2}`}</BlockMath>,
                document.getElementById('math'));