if-else statement inside jsx: ReactJS

Question

I need to change render function and run some sub render function when a specific state given,

For example:

render() {
    return (   
        

        

Answer 1

In two ways we can solve this problem:

1. Write a else condition by adding just empty <div> element.
2. or else return null.

render() {
    return (   
        <View style={styles.container}>
            if (this.state == 'news'){
                return (
                    <Text>data</Text>
                );
            }
            else {
                 <div> </div>
            }

        </View>
    )
}

Answer 2

As per DOC:

if-else statements don't work inside JSX. This is because JSX is just syntactic sugar for function calls and object construction.

Basic Rule:

JSX is fundamentally syntactic sugar. After compilation, JSX expressions become regular JavaScript function calls and evaluate to JavaScript objects. We can embed any JavaScript expression in JSX by wrapping it in curly braces.

But only expressions not statements, means directly we can not put any statement (if-else/switch/for) inside JSX.

---

If you want to render the element conditionally then use ternary operator, like this:

render() {
    return (   
        <View style={styles.container}>
            {this.state.value == 'news'? <Text>data</Text>: null }
        </View>
    )
}

Another option is, call a function from jsx and put all the if-else logic inside that, like this:

renderElement(){
   if(this.state.value == 'news')
      return <Text>data</Text>;
   return null;
}

render() {
    return (   
        <View style={styles.container}>
            { this.renderElement() }
        </View>
    )
}

Answer 3

You can do this. Just don't forget to put "return" before your JSX component.

Example:

render() {
    if(this.state.page === 'news') {
        return <Text>This is news page</Text>;
    } else {
        return <Text>This is another page</Text>;
    }
}

Example to fetch data from internet:

import React, { Component } from 'react';
import {
    View,
    Text
} from 'react-native';

export default class Test extends Component {
    constructor(props) {
        super(props);

        this.state = {
            bodyText: ''
        }
    }

    fetchData() {
        fetch('https://example.com').then((resp) => {
            this.setState({
                bodyText: resp._bodyText
            });
        });
    }

    componentDidMount() {
        this.fetchData();
    }

    render() {
        return <View style={{ flex: 1 }}>
            <Text>{this.state.bodyText}</Text>
        </View>
    }
}

Answer 4

You can achieve what you are saying by using Immediately Invoked Function Expression (IIFE)

render() {
    return (   
        <View style={styles.container}>
            {(() => {
              if (this.state == 'news'){
                  return (
                      <Text>data</Text>
                  )
              }
              
              return null;
            })()}
        </View>
    )
}

Here is the working example:

But, In your case, you can stick with the ternary operator

Answer 5

There's a Babel plugin that allows you to write conditional statements inside JSX without needing to escape them with JavaScript or write a wrapper class. It's called JSX Control Statements:

<View style={styles.container}>
  <If condition={ this.state == 'news' }>
    <Text>data</Text>
  </If>
</View>

It takes a bit of setting up depending on your Babel configuration, but you don't have to import anything and it has all the advantages of conditional rendering without leaving JSX which leaves your code looking very clean.

Answer 6

Simple example of nested loop with if condition in React:

Data example:

    menus: [
    {id:1, name:"parent1", pid: 0},
    {id:2, name:"parent2", pid: 0},
    {id:3, name:"parent3", pid: 0},
    {id:4, name:"parent4", pid: 0},
    {id:5, name:"parent5", pid: 0},
    {id:6, name:"child of parent 1", pid: 1},
    {id:7, name:"child of parent 2", pid: 2},
    {id:8, name:"child of parent 2", pid: 2},
    {id:9, name:"child of parent 1", pid: 1},
    {id:10, name:"Grand child of parent 2", pid: 7},
    {id:11, name:"Grand child of parent 2", pid: 7},
    {id:12, name:"Grand child of parent 2", pid: 8},
    {id:13, name:"Grand child of parent 2", pid: 8},
    {id:14, name:"Grand child of parent 2", pid: 8},
    {id:15, name:"Grand Child of Parent 1 ", pid: 9},
    {id:15, name:"Child of Parent 4 ", pid: 4},
    ]

Nested Loop and Condition:

    render() {
    let subMenu='';
    let ssubmenu='';
    const newMenu = this.state.menus.map((menu)=>{
    if (menu.pid === 0){
    return (
    <ul key={menu.id}>
       <li>
          {menu.name}
          <ul>
             {subMenu = this.state.menus.map((smenu) => {
             if (menu.id === smenu.pid) 
             {
             return (
             <li>
                {smenu.name}
                <ul>
                   {ssubmenu = this.state.menus.map((ssmenu)=>{
                   if(smenu.id === ssmenu.pid)
                   {
                   return(
                   <li>
                      {ssmenu.name}
                   </li>
                   )
                   }
                   })
                   }
                </ul>
             </li>
             )
             }
             })}
          </ul>
       </li>
    </ul>
    )
    }
    })
    return (
    <div>
       {newMenu}
    </div>
    );
    }
    }