---
id: children-props-type
title: Type of the Children props
layout: tips
permalink: children-props-type.html
prev: style-props-value-px.html
next: controlled-input-null-value.html
---
Usually, a component's children (`this.props.children`) is an array of components:
```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
);
```
However, when there is only a single child, `this.props.children` will be the single child component itself _without the array wrapper_ . This saves an array allocation.
```js
/** @jsx React.DOM */
var GenericWrapper = React.createClass({
componentDidMount: function() {
console.log(Array.isArray(this.props.children)); // => false
// 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);
```
