How to create guess the number game in React JS

React, a JavaScript library, is used for building the user interface of web applications by leveraging its component-based architecture.

This approach allows developers to break a web page into modular sections, making the development process more organized and scalable. Building a Guess the Number game is a practical way to gain hands-on experience with React.

This engaging yet straightforward project offers a practical way to understand how React components work together, how to manage state, and how to handle user interactions. By building this game, learners can grasp the fundamental concepts of React in a fun and interactive manner.

The main idea of this game is that the system will generate a random number and store it somewhere in a variable. Then, the user will guess that hidden number (providing the instruction by the system whether to try for a lower or higher than the current number) by multiple attempts until the correct number is guessed.

In the above code, we define a div element to contain the interface. Inside this div element:

Line 2: We use an h1 element to display the main heading “Guess the Number Game.”
Line 3: We create a button element with the text “Start New Game.” The onClick event will call the generateRandomNumber() function when the button is clicked.
Lines 4–7: We start another div element to group the input field and its label. Inside this div element.
Line 5: We use a label element with the text “Your Guess:” to describe the input field.
Line 6: We create an input element of type number to allow the user to enter their guess. The value attribute is set to the guess variable to hold the current value of the guess. The onChange event will call the handleInputChange() function when the input value changes.
Line 8: We create another button element with the text “Check Guess.” The onClick event will call the checkGuess() function when the button is clicked.
Line 9: We use a p element to display the message variable, which likely contains feedback for the user based on their guess.

Create state variables

We’ll need the following state variables to make this game executable:

To store the random hidden number to be guessed, we’ll need a number and its setNumber state variable.
To store the guessed number, another state variable guess will be required.
To display the message and to provide instructions to the user for lower or higher number, one more message state variable will be used.

In the above code:

Line 1: We use the useState hook to declare a state variable number and a function setNumber to update it. The initial value of number is an empty string ''.
Line 2: Similarly, we use the useState hook to declare another state variable guess and a function setGuess to update it. The initial value of guess is an empty string ''.
Line 3: Lastly, we use the useState hook to declare a third state variable message and a function setMessage to update it. The initial value of message is an empty string ''.

Initializing state variables with useState('') hook ensures that our game component starts with appropriate initial values, maintaining clarity and consistency in the user interface. It also helps dynamically update the feedback displayed to the user and enhances the game’s interactive and instructional aspects.

Implement functionalities

Now we’ll create the functions required for this game development. Let’s discuss them one by one:

generateRandomNumber(): Once the game gets started, a random number will be generated by the system using Math.random the function.
checkGuess(): Every time the user enters a new number, we’ll verify whether this number is lower, higher, or equal to the generated random number and provide the instructions respectively.
handleInputChange(): An input handler to set the number (entered by the user) in the input field.

const generateRandomNumber = () => {
    // Generate a random number between 1 and 100
    const randomNumber = Math.floor(Math.random() * 100) + 1;
    setNumber(randomNumber);
    setMessage('');
  };
const checkGuess = () => {
    if (guess === '') {
        setMessage('Please enter a number.');
    } else {
        const userGuess = parseInt(guess);
        if (userGuess === number) {
            setMessage('Congratulations! You guessed the correct number.');
        } else if (userGuess < number) {
            setMessage('Try a higher number.');
        } else {
            setMessage('Try a lower number.');
        }
    }
};
const handleInputChange = (event) => {
    setGuess(event.target.value);
};

In the above code:

Lines 1–6: We define the generateRandomNumber() function. Inside this function:
- Line 2: We generate a random number between 1 and 100. For this, we use the Math.random() method, and multiply the result by 100. We call the Math.floor() method to take the floor value and add 1.
- Line 3: We call the setNumber() method to update the number state with this randomly generated number.
- Line 4: We call the setMessage() method to reset the message state to an empty string.
Lines 8–21: We define the checkGuess() function. Inside this function:
- Line 9–10: We check if the guess state is an empty string. If the guess is empty, we call the setMessage() method to update the message state to “Please enter a number.”.
- Line 12: Otherwise, if the guess is not empty, we use the parseInt() method to parse it to an integer and store it in the userGuess variable.
- Lines 13–14: We check if the userGuess is equal to the number. If it is, we call the setMessage() method to update the message state to “Congratulations! You guessed the correct number.”
- Lines 15–16: If the userGuess is less than the number, we call the setMessage() method to update the message state to “Try a higher number.”
- Lines 17–18: If the userGuess is greater than the number, we call the setMessage() method to update the message state to “Try a lower number.”
Lines 23–25: We define the handleInputChange() function. Inside this function:
- Line 24: We call the setGuess() method to update the guess state with the value of the input field.