Applying Custom Formatting

In the previous guide we learned how to create custom block types that render chunks of text inside different containers. But Slate allows for more than just "blocks".

In this guide, we'll show you how to add custom formatting options, like bold, italic, code or strikethrough.

So we start with our app from earlier:

class App extends React.Component {

state = {
value: initialValue,
}

onChange = ({ value }) => {
this.setState({ value })
}

onKeyDown = (event, change) => {
if (event.key != '`' || !event.metaKey) return
event.preventDefault()
const isCode = change.value.blocks.some(block => block.type == 'code')

change.setBlock(isCode ? 'paragraph' : 'code')
return true
}

render() {
return (
<Editor
value={this.state.value}
onChange={this.onChange}
onKeyDown={this.onKeyDown}
renderNode={this.renderNode}
/>
)
}

renderNode = (props) => {
switch (props.node.type) {
case 'code': return <CodeNode {...props} />
}
}

}

And now, we'll edit the onKeyDown handler to make it so that when you press ⌘-B, it will add a "bold" mark to the currently selected text:

class App extends React.Component {

state = {
value: initialValue,
}

onChange = ({ value }) => {
this.setState({ value })
}

onKeyDown = (event, change) => {
if (!event.metaKey) return

// Decide what to do based on the key code...
switch (event.key) {
// When "B" is pressed, add a "bold" mark to the text.
case 'b': {
event.preventDefault()
change.addMark('bold')
return true
}
// When "`" is pressed, keep our existing code block logic.
case '`': {
const isCode = change.value.blocks.some(block => block.type == 'code')
event.preventDefault()
change.setBlock(isCode ? 'paragraph' : 'code')
return true
}
}
}

render() {
return (
<Editor
value={this.state.value}
onChange={this.onChange}
onKeyDown={this.onKeyDown}
renderNode={this.renderNode}
/>
)
}

renderNode = (props) => {
switch (props.node.type) {
case 'code': return <CodeNode {...props} />
}
}

}

Okay, so we've got the hotkey handler setup... but! If you happen to now try selecting text and hitting ⌘-B, you'll get an error in your console. That's because we haven't told Slate how to render a "bold" mark.

For every mark type you want to add to your schema, you need to give Slate a "renderer" for that mark, just like nodes. So let's define our bold mark:

// Define a React component to render bold text with.
function BoldMark(props) {
return <strong>{props.children}</strong>
}

Pretty simple, right?

And now, let's tell Slate about that mark. To do that, we'll pass in the renderMark prop to our editor. Also, let's allow our mark to be toggled by changing addMark to toggleMark.

function BoldMark(props) {
return <strong>{props.children}</strong>
}

class App extends React.Component {

state = {
value: initialValue,
}

onChange = ({ value }) => {
this.setState({ value })
}

onKeyDown = (event, change) => {
if (!event.metaKey) return

switch (event.key) {
case 'b': {
event.preventDefault()
change.toggleMark('bold')
return true
}
case '`': {
const isCode = change.value.blocks.some(block => block.type == 'code')
event.preventDefault()
value.setBlock(isCode ? 'paragraph' : 'code')
return true
}
}
}

render() {
return (
<Editor
value={this.state.value}
onChange={this.onChange}
onKeyDown={this.onKeyDown}
renderNode={this.renderNode}
// Add the `renderMark` prop...
renderMark={this.renderMark}
/>
)
}

renderNode = (props) => {
switch (props.node.type) {
case 'code': return <CodeNode {...props} />
}
}

// Add a `renderMark` method to render marks.
renderMark = (props) => {
switch (props.mark.type) {
case 'bold': return <BoldMark {...props} />
}
}

}

Now, if you try selecting a piece of text and hitting ⌘-B you should see it turn bold! Magic!

Was this page helpful? Let us know how we did: