Creating a simple hashtag formatter in React Native

Question

Is it possible, without using external libraries, to parse a string with hashtag then style it with the Text component?

const string = "Let's #Tweet on #Twitter";

// Expect:
// Let's <Text style={{ color: 'blue' }}>#Tweet</Text> on <Text style={{ color: 'blue' }}>#Twitter</Text>

I thought this would do:

import React from 'react';
import { Text } from 'react-native';

export const HASHTAG_FORMATTER = string => {
  return string.replace(/(^|\s)(#[a-z\d-]+)/ig, `$1${<Text style={{ color: 'blue' }}>$2</Text>}`);
}

Usage:

import React from 'react';
import { View, Text } from 'react-native';
import { HASHTAG_FORMATTER } from '../../utilities/hashtag';

const Home = props => {
  return (
    <View>
      <Text>{HASHTAG_FORMATTER("Let's #Tweet on #Twitter")}</Text>
    <View>
  )
}

What I got instead was:

Let's [object Object] on [object Object]

See example: https://codesandbox.io/s/react-native-69dwm?fontsize=14

Is there a way to achieve this in jsx? Thanks.

Answer 1

You can't use back references like this, you can use callback function of replace when you want to have a dynamic evaluation

const HASHTAG_FORMATTER = string => {
  return string.replace(/(^|\s)(#[a-z\d-]+)/ig, (m, g1, g2) => {
    return g1 + "<span style={color:'green'}>" + g2 + "< /span>"
  });
}


console.log(HASHTAG_FORMATTER("#tweet"))

To solve your specific problem you need to solve it by splitting string and then building Text components as per the values

Demo

const HASHTAG_FORMATTER = string => {
  return string.split(/((?:^|\s)(?:#[a-z\d-]+))/gi).filter(Boolean).map((v,i)=>{
    if(v.includes('#')){
      return <Text key={i} style={{color:'green'}}>{v}</Text>
    }   else{
      return <Text key={i}>{v}</Text>
    }
  })
};