How to render random objects from an array in React?

Question

I just started learning React in my work and I need to build a blog using React. I need to show random posts as "recommended Posts", after doing some research I found a possible solution, using Math.random() but I could not figure it out how to implement it in my component.

This is my code:

RecommendedPost/index.js

import React from 'react';
import { Link } from 'react-router';

class RecommendedPosts extends React.Component {

render() {
return (
  <ul>
    {this.props.posts.map((post, idx) => {
      return (
        <li key={idx}>
          <p>{post.title}</p>
          <p>{post.text}</p>
          <p>{post.category}</p>
          <Link to={`/blog/post-1/:${post.id}`}>Weiter lesen</Link>
        </li>
      );
    })}
  </ul>
);
}
}
RecommendedPosts.propTypes = {
posts: React.PropTypes.array,
};
export default RecommendedPosts;

Then I use this component in my container: BlogPage/SinglePostPage/index.js

import React from 'react';
// ...other imported stuff
import RecommendedPosts from 'components/Blog/RecommendedPosts';

class PostPage extends React.Component {

render() {
  // dummy-recomended-posts
const posts = [
  {
    id: 1,
    title: 'How to Cook Blue Meth',
    description: 'Lorem ipsum dolor sit amet, turpis at, elit',
    thump: 'thump.jpg',
    hero: '/img/',
    category: 'k1',
    fullname: 'Walter White',
    published: '10.05.2016, 15:30pm',
  },
  {
    id: 2,
    title: 'Passenger',
    description: 'Lorem ipsum dolor sit amet, turpis at, elit',
    thump: 'thump.jpg',
    hero: '/img/',
    category: 'k2',
    fullname: 'Chino Moreno',
    published: '10.05.2016, 15:30pm',
   },
    // ...and more dummy posts(about 7)
   ];
return (
   <div>
   // here, I pass the posts array to my component
   <RecommendedPosts posts={posts} />
   </div>
  );
  }
 }
}
export default connect(null, mapDispatchToProps)(PostPage);

My idea is to render the posts randomly using the id as a ref but again I can't find the way.

Hope some one can help me, and sorry if the answer is too obvious for everyone.

Grgur · Accepted Answer · 2019-11-21 12:14:07Z

19

I went ahead and created a working example for you

import React from 'react';
import { Link } from 'react-router';

function shuffleArray(array) {
  let i = array.length - 1;
  for (; i > 0; i--) {
    const j = Math.floor(Math.random() * (i + 1));
    const temp = array[i];
    array[i] = array[j];
    array[j] = temp;
  }
  return array;
}

class RecommendedPosts extends React.Component {
  render() {
    const shuffledPosts = shuffleArray(this.props.posts);
    return (
      <ul>
        {shuffledPosts.map((post) => {
          return (
            <li key={post.id}>
              <p>{post.title}</p>
              <p>{post.text}</p>
              <p>{post.category}</p>
              <Link to={`/blog/post-1/:${post.id}`}>Weiter lesen</Link>
            </li>
          );
        })}
      </ul>
    );
  }
}
RecommendedPosts.propTypes = {
  posts: React.PropTypes.array,
};
export default RecommendedPosts;

Bonus tip - since you're not using state or lifecycle, you can create a much simpler functional component as such:

import React from 'react';
import { Link } from 'react-router';

function shuffleArray(array) {
  let i = array.length - 1;
  for (; i > 0; i--) {
    const j = Math.floor(Math.random() * (i + 1));
    const temp = array[i];
    array[i] = array[j];
    array[j] = temp;
  }
  return array;
}

function RecommendedPosts({ posts }) {
  const shuffledPosts = shuffleArray(posts);
  return (
    <ul>
      {shuffledPosts.map((post) => {
        return (
          <li key={post.id}>
            <p>{post.title}</p>
            <p>{post.text}</p>
            <p>{post.category}</p>
            <Link to={`/blog/post-1/:${post.id}`}>Weiter lesen</Link>
          </li>
        );
      })}
    </ul>
  );
}
RecommendedPosts.propTypes = {
  posts: React.PropTypes.array,
};
export default RecommendedPosts;

edited Nov 21, 2019 at 12:14

answered Jun 29, 2016 at 15:22

Grgur

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2 Comments

Marco Chavez Over a year ago

That was just amazing! Thank you so much!....and also thanks to everyone who help to improve this question! I guess I have a lot to learn and I want to try doing this with states and lifecycles!

Harsh kurra Over a year ago

key={idx} will cause un-mounting and re-mounting of the child component on every re-render of RecommendedPosts, we can avoid that if we use fixed Key for each child(let's say original index of each child)

Piyush.kapoor · Accepted Answer · 2016-06-29 13:50:11Z

3

In your Recommended post first shuffle the posts and store it in state and then render

import React from 'react';
import { Link } from 'react-router';

class RecommendedPosts extends React.Component {

constructor() {
super(props);
this.state = {
posts: this.shuffle(this.props.posts)
}
}

shuffle(posts){
 ///shuffle using some algo
return posts
}

render() {
return (
  <ul>
    {this.state.posts.map((post, idx) => {
      return (
        <li key={idx}>
          <p>{post.title}</p>
          <p>{post.text}</p>
          <p>{post.category}</p>
          <Link to={`/blog/post-1/:${post.id}`}>Weiter lesen</Link>
        </li>
      );
    })}
  </ul>
);
}
}
RecommendedPosts.propTypes = {
posts: React.PropTypes.array,
};
export default RecommendedPosts;

answered Jun 29, 2016 at 13:50

Piyush.kapoor

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1 Comment

Brandon Over a year ago

using props in your constructor is an antipattern. Just shuffle the posts at the top of render: const postsToRender = this.shuffle(this.props.posts). If you really want to store it in state, then do the shuffling in componentWillMount and componentWillReceiveProps

Vikramaditya · Accepted Answer · 2016-06-29 14:11:52Z

1

you can use lodash shuffle function to randomize your array and then simply render by taking data from that array.

answered Jun 29, 2016 at 14:11

Vikramaditya

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