ex for entry 7
This commit is contained in:
parent
9471287794
commit
7d50ab600f
|
@ -7,6 +7,41 @@ prev: style-prop-value-px.html
|
|||
next: controlled-input-null-value.html
|
||||
---
|
||||
|
||||
Usually, a component's `this.props.children` is an array of components. To save an extra array allocation, it returns the component itself when there's only one.
|
||||
Usually, a component's `this.props.children` is an array of components:
|
||||
|
||||
This means accessing, for example, `this.props.children.length` might be misleading, as it could either be the `length` property of the array of children, or that of a single string component.
|
||||
```js
|
||||
/** @jsx React.DOM */
|
||||
|
||||
var GenericWrapper = React.createClass({
|
||||
componentDidMount: function() {
|
||||
console.log(Array.isArray(this.props.children)); // => true
|
||||
},
|
||||
render: function() {
|
||||
return <div />;
|
||||
}
|
||||
});
|
||||
|
||||
React.renderComponent(
|
||||
<GenericWrapper><span/><span/><span/></GenericWrapper>,
|
||||
mountNode
|
||||
);
|
||||
```
|
||||
|
||||
To save an extra array allocation, it returns the component itself _without the array wrapper_ when there's only one child.
|
||||
|
||||
```js
|
||||
/** @jsx React.DOM */
|
||||
|
||||
var GenericWrapper = React.createClass({
|
||||
componentDidMount: function() {
|
||||
// **warning**: yields 5 for length of the string 'hello', not 1 for the
|
||||
// length of the non-existant array wrapper!
|
||||
console.log(this.props.children.length);
|
||||
},
|
||||
render: function() {
|
||||
return <div />;
|
||||
}
|
||||
});
|
||||
|
||||
React.renderComponent(<GenericWrapper>hello</GenericWrapper>, mountNode);
|
||||
```
|
||||
|
|
Loading…
Reference in New Issue