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Tweaks to if-else tip

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Paul O’Shannessy 11 years ago
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      tips/03-if-else-in-JSX.md

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tips/03-if-else-in-JSX.md

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--- ---
`if-else` statements don't work inside JSX, since JSX is really just sugar for functions: `if-else` statements don't work inside JSX. This is because JSX is just syntactic sugar for function calls and object construction. Take this basic example:
```js ```js
/** @jsx React.DOM */ /** @jsx React.DOM */
// this // This JSX:
React.renderComponent(<div id="msg">Hello World!</div>, mountNode); React.renderComponent(<div id="msg">Hello World!</div>, mountNode);
// is the same as this
// Is transformed to this JS:
React.renderComponent(React.DOM.div({id:"msg"}, "Hello World!"), mountNode); React.renderComponent(React.DOM.div({id:"msg"}, "Hello World!"), mountNode);
``` ```
Which means `<div id={if (true){ 'msg' }}>Hello World!</div>` doesn't make sense, as (if it worked) it would be compiled down to something like this `React.DOM.div({id: if (true){ 'msg' }}, "Hello World!")`, which isn't valid JS. This means that `if` statements don't fit in. Take this example:
```js
/** @jsx React.DOM */
// This JSX:
<div id={if (condition) { 'msg' }}>Hello World!</div>
// Is transformed to this JS:
React.DOM.div({id: if (condition) { 'msg' }}, "Hello World!");
```
What you're searching for is ternary expression: That's not valid JS. You probably want to make use of a ternary expression:
```js ```js
/** @jsx React.DOM */ /** @jsx React.DOM */
React.renderComponent(<div id={true ? 'msg' : ''}>Hello World!</div>, mountNode); React.renderComponent(<div id={condition ? 'msg' : ''}>Hello World!</div>, mountNode);
``` ```
Try the [JSX compiler](/react/jsx-compiler.html). Try using it today with the [JSX compiler](/react/jsx-compiler.html).

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