react useeffect functional update 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: useeffect on update

const isInitialMount = useRef(true);

useEffect(() => {
  if (isInitialMount.current) {
     isInitialMount.current = false;
  } else {
      // Your useEffect code here to be run on update
  }
});

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>;
};