Syntax Error - Condition Statement in React js Render [duplicate]

Question

i am new to REACT.js and your advise would be much appreciated

i have a list of categories i have placed a post under
i would like to display categories only if there are categories present
i am unsure why i am getting a syntax error - looked through it over and over

i tried the below:

<span className="categories">
  {
    if (post.categories) {
      Object.values(post.categories).slice(0, 1).map((category) => {
        return(
          <span>{category.name}</span>
        );
      })
    } else {
      return null;
    } 
  }
</span>

but i get the error: Failed to compile

BELOW ARE MY FILES

app/scr/components/Blog/Index.js

import Layout from '../../components/Layout/Layout';
import { Link } from 'react-router-dom';
    
class Index extends Component {
  render() {
    return(
      <Layout>
        <ul>
          {this.props.posts.map((post) => {
            if (post) {
              return(
                <li key={post.ID} className="card">
                  <div>{post.title}</div>
                  <div>{post.date}</div>
                  <span className="categories">
                    {
                      if (post.categories) {
                        Object.values(post.categories).slice(0, 1).map((category) => {
                          return(
                            <span>{category.name}</span>
                          );
                        })
                      } else {
                        return null;
                      } 
                    }
                  </span>
                </li>
              );
            } else {
              return null;
            }
          })}
        </ul>
      </Layout>
    );
  }
}

export default Index;

reactjs.org/docs/… you are not using the if statememnt correctly — Cornel Raiu
– Cornel Raiu, Commented Aug 18, 2020 at 21:54
More broadly: you can only interpolate JavaScripts expressions, not statements, in JSX (although they can be function expressions, which can have a body containing statements...). Think about what JS that JSX would be transpiled to and it should become obvious why. — jonrsharpe
– jonrsharpe, Commented Aug 18, 2020 at 22:04

Cornel Raiu · Accepted Answer · 2020-08-18 21:56:09Z

1

You are not using the inline conditional correctly.

You should do it like this:

<span className="categories">
  {post.categories ?
    Object.values(post.categories).slice(0, 1).map((category) => {
      return(
        <span>{category.name}</span>
      );
    }) : null}
</span>

You can read more about conditionals in React here and more specifically about inline conditionals here

answered Aug 18, 2020 at 21:56

Cornel Raiu

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