How do you generate random items from an array without repeating in React.js?

Question

Below is a snippet of my code.. I'm working on a random quote generator and would like to find a solution on generating each random quote and background from the arrays without repeats until all have been used, and then cycling through again. The background images are being imported directly into the state and the quote array is imported from a separate file. I've attempted slicing each item from the array and pushing it into an empty one, but so far that has been unsuccessful.

   constructor(props) {
        super(props);
        
        this.state = {
            quote: quotes[0].quote,
            author: quotes[0].author,
            backgrounds: [
                photos..
            ]
        };
    }
    
    
    shuffleAll = (arr) => {
        return arr.sort(function () { return 0.5 - Math.random() });
    }
    
    findRandomQuote = (arr) => {
        let num = Math.floor(Math.random() * quotes.length);
        let randQuote = quotes[num];
        this.shuffleAll(quotes);
        this.setState({
            quote: randQuote.quote,
            author: randQuote.author
        });
    }

    findRandomBackground = (arr) => {
        const { backgrounds } = this.state;
        let background = backgrounds[Math.floor(Math.random() * backgrounds.length)];
        this.shuffleAll(backgrounds);
        document.body.style.background = `url(${background})`;
    }

What is quotes? Please try creating a minimal reproducible example — T J
– T J, Commented Apr 30, 2021 at 15:16
"I've attempted slicing each item from the array and pushing it into an empty one" - Please also share the code that you've attempted — T J
– T J, Commented Apr 30, 2021 at 15:20
quotes is being imported in from a separate file holding my quotes array, which has both the quote and author in each index. previously I have tried adding another item to state such as usedQuotes = [ ] , and then after setting state I added quotes.slice(randQuote).push(this.usedQutoes) to the function findRandomQuote, but that did not work. — jsdev
– jsdev, Commented May 18, 2021 at 20:08

Steven Hardy · Accepted Answer · 2021-04-30 21:22:10Z

1

You can use state to store the quote array, and substract from it until all quotes are used up:

constructor(props) {
    super(props);
    this.state = {
        availableQuotes: [...quotes],
        activeQuote: null
    };
}

findRandomQuote = () => {
    const quoteOptions = this.state.availableQuotes.length > 0 ? this.state.availableQuotes : quotes;
    const randomIndex = Math.floor(Math.random() * quoteOptions.length);
    this.setState({
        availableQuotes: [...quoteOptions].splice(randomIndex, 1),
        activeQuote: quoteOptions[randomIndex]
    });
}


// This runs after component mounts, to set the first random quote
componentDidMount() { 
    this.findRandomQuote();
}

You can do a similar thing to randomise the background images.

edited Apr 30, 2021 at 21:22

answered Apr 30, 2021 at 15:52

Steven Hardy

1117 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

jsdev Over a year ago

I haven't quite gotten this solution to work with my code, but adding componentDidMount fixed another issue I've had with rendering the first random quote on page load, so thank you!!

Collectives™ on Stack Overflow

How do you generate random items from an array without repeating in React.js?

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest