Can a component return a value?

Can a component return a value?

React’s one-way data-binding model means that child components cannot send back values to parent components unless explicitly allowed to do so. The React way of doing this is to pass down a callback to the child component (see Facebook’s “Forms” guide).

Can a component return null?

Yes you can, but instead of blank, simply return null if you don’t want to render anything from component, like this: return (null); Another important point is, inside JSX if you are rendering element conditionally, then in case of condition=false , you can return any of these values false, null, undefined, true .

How do I return an empty React component?

How do you return a component value?

You can use a reference to the mounted component to get its state: var Slider = React. createClass({ getInitialState: function() { return { sliderValue: 5 }; }, render: function() { return ; } }); var mySlider = ReactDOM.

How do I return multiple components in React?

In React v16 it’s possible for render() to return an array of elements. Another option is to use a Fragment. Fragments let you group a list of children without adding extra nodes to the DOM.

How do you’re-render React component?

4 methods to force a re-render in React

1. Re-render component when state changes. Any time a React component state has changed, React has to run the render() method.
2. Re-render component when props change.
3. Re-render with key prop.
4. Force a re-render.
5. Conclusion.

Why does enumerable all return true for an empty list?

And is the same reason All (which can be thought of as the repeated application of the logical AND operator) will return true when the list is empty ( p && true is equivalent to p ), and the same reason Any (the OR operator) will return false.

Why does all return true for all elements?

All requires the predicate to be true for all elements of the sequence. This is explicitly stated in the documentation. It’s also the only thing that makes sense if you think of All as being like a logical “and” between the predicate’s results for each element.

Why does all return true for an empty sequence?

Likewise, the false you get from Any for the empty sequence is the identity for logical “or”. If you think of All as “there are no elements in the sequence that are not”, this might make more sense. It is true, as nothing (no condition) makes it false. The docs probably explain it.

When to return NULL or an empty object?

Returning null is usually the best idea if you intend to indicate that no data is available. An empty object implies data has been returned, whereas returning null clearly indicates that nothing has been returned.