JSX (sometimes referred to as JavaScript XML) is an XML-like extension to the JavaScript language syntax. Initially created by Facebook for use with React, JSX has been adopted by multiple web frameworks.: 5 : 11 Being a syntactic sugar, JSX is generally transpiled into nested JavaScript function calls structurally similar to the original JSX.
Markup
An example of JSX code:
const App = () => { return ( <div> <p>Header</p> <p>Content</p> <p>Footer</p> </div> ); }Nested elements
Multiple elements on the same level need to be wrapped in a single React element such as the <div> element shown above, a fragment delineated by <Fragment> or in its shorthand form <>, or returned as an array.456: 68–69
Attributes
JSX provides a range of element attributes designed to mirror those provided by HTML. Custom attributes can also be passed to the component.7 All attributes will be received by the component as props.
JavaScript expressions
JavaScript expressions (but not statements) can be used inside JSX with curly brackets {}:8: 14–16
<h1>{10+1}</h1>The example above will render:
<h1>11</h1>Conditional expressions
If–else statements cannot be used inside JSX but conditional expressions can be used instead. The example below will render { i === 1 ? 'true' : 'false' } as the string 'true' because i is equal to 1.
const App = () => { const i = 1; return ( <div> <h1>{ i === 1 ? 'true' : 'false' }</h1> </div> ); }The above will render:
<div> <h1>true</h1> </div>Functions and JSX can be used in conditionals:9: 88–90
const App = () => { const sections = [1, 2, 3]; return ( <div> {sections.map((n,i) => ( /* 'key' is used by React to keep track of list items and their changes */ /* Each 'key' must be unique */ <div key={"section-" + n}> Section {n} {i === 0 && <span>(first)</span>} </div> ))} </div> ); }The above will render:
<div> <div>Section 1<span>(first)</span></div> <div>Section 2</div> <div>Section 3</div> </div>Code written in JSX requires conversion with a tool such as Babel before it can be understood by web browsers.1011: 5 This processing is generally performed during a software build process before the application is deployed.
See also
External links
References
"Draft: JSX Specification". JSX. Facebook. Retrieved 7 April 2018. https://facebook.github.io/jsx/ ↩
Larsen, John (2021). React Hooks in Action With Suspense and Concurrent Mode. Manning. ISBN 978-1720043997. 978-1720043997 ↩
Wieruch, Robin (14 September 2018). The Road to React. Leanpub. ISBN 978-1720043997. 978-1720043997 ↩
Clark, Andrew (September 26, 2017). "React v16.0§New render return types: fragments and strings". React Blog. https://reactjs.org/blog/2017/09/26/react-v16.0.html#new-render-return-types-fragments-and-strings ↩
"React.Component: render". React. https://reactjs.org/docs/react-component.html#render ↩
Wieruch, Robin (14 September 2018). The Road to React. Leanpub. ISBN 978-1720043997. 978-1720043997 ↩
Clark, Andrew (September 26, 2017). "React v16.0§Support for custom DOM attributes". React Blog. https://reactjs.org/blog/2017/09/26/react-v16.0.html#support-for-custom-dom-attributes ↩
Wieruch, Robin (14 September 2018). The Road to React. Leanpub. ISBN 978-1720043997. 978-1720043997 ↩
Wieruch, Robin (14 September 2018). The Road to React. Leanpub. ISBN 978-1720043997. 978-1720043997 ↩
Fischer, Ludovico (2017-09-06). React for Real: Front-End Code, Untangled. Pragmatic Bookshelf. ISBN 9781680504484. 9781680504484 ↩
Larsen, John (2021). React Hooks in Action With Suspense and Concurrent Mode. Manning. ISBN 978-1720043997. 978-1720043997 ↩