如何使用 onClick 更改容器的背景颜色？

Question

I am using Next.js. I have a set of colors in a different file. How do I change it randomly using onClick ?

The Color.js file

export const Colors = [
    "#16a085",
    "#27ae60",
    "#2c3e50",
    "#f39c12",
    "#e74c3c",
    "#9b59b6",
    "#FB6964",
    "#342224",
    "#472E32",
    "#BDBB99",
    "#77B1A9",
    "#73A857",
];

The Main file

import { Colors } from "./Colors.js";

export default function Home() {
    const randomColor = Math.floor(Math.random() * 12);
    const [color, setColor] = useState(Colors);
    console.log(color);
    const changeColor = () => {       
         setColor(color[randomColor]);   
    };

The Error:

Unhandled Runtime Error
TypeError: Cannot read properties of undefined (reading '9')

Answer 1

You have made 3 mistakes in your code.

First you have created color state with whole color array that you have imported.

But instead use one default or empty value as below

const [color, setColor] = React.useState("#16a085");

The next mistake is to you are fetching index from the state color which is not an array once you click on the button it becomes a string and it will index out of bound as no color string has length greater than 7

It can be fixed by

setColor(Colors[randomColor]);

Now you will get rid of the error but the color won't change because your random number generator is outside and it is generate when the component updates so fix will be to place it inside the function.

The final code I guess will look as below

import { Colors } from "./Colors";

export default function App() {
  const [color, setColor] = React.useState("#16a085");
  const changeColor = () => {
    const randomColor = Math.floor(Math.random() * 12);
    setColor(Colors[randomColor]);
  };
  return (
    <div className="App">
      <div style={{ color: color }}>hello</div>
      <button onClick={changeColor}>change</button>
    </div>
  );
}