useRef
/*
A common use case is to access a child imperatively:
*/
function TextInputWithFocusButton() {
const inputEl = useRef(null);
const onButtonClick = () => {
// `current` points to the mounted text input element
inputEl.current.focus();
};
return (
<>
<input ref={inputEl} type="text" />
<button onClick={onButtonClick}>Focus the input</button>
</>
);
}react usecontext examples
import React from "react";
import ReactDOM from "react-dom";
// Create a Context
const NumberContext = React.createContext();
// It returns an object with 2 values:
// { Provider, Consumer }
function App() {
// Use the Provider to make a value available to all
// children and grandchildren
return (
<NumberContext.Provider value={42}>
<div>
<Display />
</div>
</NumberContext.Provider>
);
}
function Display() {
// Use the Consumer to grab the value from context
// Notice this component didn't get any props!
return (
<NumberContext.Consumer>
{value => <div>The answer is {value}.</div>}
</NumberContext.Consumer>
);
}
ReactDOM.render(<App />, document.querySelector("#root"));
//now with useContext the same page look like this
// import useContext (or we could write React.useContext)
import React, { useContext } from 'react';
// ...
function Display() {
const value = useContext(NumberContext);
return <div>The answer is {value}.</div>;
}useContext
const value = useContext(MyContext);Copyright © 2021 Codeinu
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