useCallback code example

Example 1: 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>
    </>
  );
}

Example 2: use callback vs use memo

// They both take a function and an array of dependencies:

useCallback(() => {···}, [dependency1, dependency2]);
useMemo(() => {···}, [dependency1, dependency2]);

// So what is the difference? 

// useCallback returns its function uncalled so you can call it later
// therefore, it gives you back the function's reference

// useMemo calls its function and returns the result.
// therefore, it gives you back the function's return value

Example 3: usecontext hook

import React, { useContext } from "react";
import ColorContext from "./colorcontex.ts";

const MyComponent = () => {
  const colors = useContext(ColorContext);

  return <div style={{ backgroundColor: colors.blue }}>...</div>;
};import React, { useContext } from "react";

const MyComponent = () => {
  const colors = useContext(ColorContext);

  return <div style={{ backgroundColor: colors.blue }}>...</div>;
};