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Build Weather App With React

thangdc1982 profile image Thang Cam Duong ・6 min read

Demo

Source code

Here

Introduction

In this article, we will learn to build the weather app using

  1. React function component
  2. React hooks
  3. React data management context api

Prerequiestes

  • Install Visual Studio Code (VS Code) from here
  • Install NodeJS from here
  • Create account for open weather api here

Create project

Create weather app project

npx create-react-app weather-app
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The command above will create a new React project with the name weather-app

Change the directory to the new project

cd weather-app
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Let run the application to make sure, the project was created successfully by using the command

npm start
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Install the dependencies

I am using the feather icons for any icons using in the project. All the icons can be found here
To add the feather icons to the react prject we are using the command

npm i react-feather
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The usage for react-feather icon can be seen here

Open the project in VS Code

Open the project in VS Code

code .
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Update the CSS style

Because this is a simple project, therefore I put all the style code in one single file App.css.
Replace all the content in the App.css with the content from App.css

Create reducers

Make a new folder reducers under the src directory.
Then make a new index.js under the reducers folder.
Copy the following code the index.js file

export const getWeather = async (api) => {
    const response = await fetch(api);
    if (!response.ok) {
        // throw an error if response has not successed
      throw new Error(`${response.status}, ${response.statusText}`);
    } else {
        return await response.json();
    }
}

export const updateWeather = (dispatch, data) => {
    let weather = {};
    weather.temprature = {
        unit: "celsius"
    };
    weather.temprature.value = Math.floor(data.main.temp - KELVIN);
    weather.description = data.weather[0].description;
    weather.iconId = `http://openweathermap.org/img/w/${data.weather[0].icon}.png`;
    weather.city = data.name;
    weather.country = data.sys.country;          


    dispatch({
        type: "UPDATE_WEATHER",
        payload: weather
    });
};

export const KEY = "This is the key from your account openweather";

export const KELVIN = 273;

const reducer = (state, action) => {
    const { type, payload } = action;        
    switch (type) {                     
        case "SET_ERROR": 
            return {
                ...state,
                error: payload.error,
                city: payload.city,
                weather: null
            };
        case "SET_LOCATION":
            return {
                ...state,
                latitude: payload.latitude,
                longitude: payload.longitude
            };
        case "UPDATE_WEATHER":
            return {
                ...state,                
                weather: payload,
                error: null,
                city: payload.city
            };
        default:
            return state;
    }
};

export default reducer;
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  • getWeather is to perform the async event to get the data from the open weather with the provided URL as the parameters
  • updateWeather takes the dispatch method, and the data return from the getWeather to format data as desired and dispatch the method to update the state values.
  • reducer is defining all the action and payload data to update to the state. There are a total of three actions here
  • SET_ERROR will notify the component to display the error message if fails to get the weather
  • SET_LOCATION will set the latitude and longitude value from your current location, this is a one-time set. The values will be reused when the location icon is clicked
  • UPDATE_WEATHER update the weather information in the state so they will be displayed in the component # Create StateProvide (store) Make a new folder store under the src directory. Then make a new index.js under the store folder. Copy the following code the index.js file
import React, { createContext, useContext, useReducer } from 'react';
import reducer from '../reducers';

export const initialState = {
    weather: null,
    latitude: 0.0,
    longitude: 0.0,
    city: "",
    error: null
};

export const StateContext = createContext(initialState);
const { Provider } = StateContext;

export const StateProvider = ({children}) => {
    return <Provider value={useReducer(reducer, initialState)}>{children}</Provider>;
};

export const useStateValue = () => useContext(StateContext);
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  • initialState is the initial values of the state
  • reducer is defined from our reducers
  • useContext returns the current context value for that context. # Make use of StateProvide Open the index.js under the src folder, and update the script content as below
import React from 'react';
import ReactDOM from 'react-dom';
import './index.css';
import App from './App';
import reportWebVitals from './reportWebVitals';
import { StateProvider } from './store';

ReactDOM.render(
  <React.StrictMode>
    <StateProvider>
      <App />
    </StateProvider>
  </React.StrictMode>,
  document.getElementById('root')
);

// If you want to start measuring performance in your app, pass a function
// to log results (for example: reportWebVitals(console.log))
// or send to an analytics endpoint. Learn more: https://bit.ly/CRA-vitals
reportWebVitals();
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App component is now surrounded by our StateProvider. This will make the state available for the whole application.

Adding Notification component

Notification component is to display the error message.
Create a new file Notification.js under the src directory

import React from 'react';
import { useStateValue } from './store';

function Notification() {    

    const [{error, city}] = useStateValue();  

    return (
        <div className="notification">
            {error && <p>{error.message}, <b><i>"{city}"</i></b> is not a valid city</p>}
        </div>
    )
}

export default Notification

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const [{error, city}] = useStateValue(); allows to access the data from the global state.

Adding Header/City component

Header/City component is to display the title message, and the input field to allow user to enter the city name. it is also included the button icon to allow re-set the location back to the current location of the user machine.
Create a new file City.js under the src directory

import React, { useState, useEffect } from 'react';
import { MapPin } from 'react-feather';
import { useStateValue } from './store';
import { getWeather, KEY, updateWeather } from './reducers';

function CityInfo() {
    const [currentCity, setCurrentCity] = useState('');
    const [{city, latitude, longitude}, dispatch] = useStateValue();    

    useEffect(() => {
        setCurrentCity(city);
    }, []);

    /**
     * Use click on the location button to see the weather
     * at the current location
     */
    const defaultLocation = () => {
        let api = `http://api.openweathermap.org/data/2.5/weather?lat=${latitude}&lon=${longitude}&appid=${KEY}`;
        getWeatherData(api);
    };

    /**
     * Key up event to capture keyboard
     * Firing to update the city in the store if the key is Enter
     */
    const onCityChange = (event) => {
        if (event.keyCode === 13) {
            event.preventDefault();           
            let api = `http://api.openweathermap.org/data/2.5/weather?q=${currentCity}&appid=${KEY}`;    
            getWeatherData(api);
        }
    };

    const getWeatherData = (api) => {
        getWeather(api)
        .then((data) => {    
            setCurrentCity(data.name); 
            updateWeather(dispatch, data);
        })
        .catch (e => {            
            dispatch({
                type: "SET_ERROR",
                payload: {
                    error: e,
                    city: currentCity
                }
            }); 
        }); 
    };

    /**
     * Handle the input change
     */
    const handleChange = (event) => {
        setCurrentCity(event.target.value);
    }

    return (
        <div className="app-title">
            <p>Weather Info</p>
            <input type="text" placeholder="Enter the city" autoComplete="off" 
            onChange={handleChange}
            value={currentCity} onKeyUp={onCityChange} />
            <div className="location-icon" onClick={defaultLocation}>
                <MapPin />
            </div>        
        </div>
    )
}

export default CityInfo;
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const [currentCity, setCurrentCity] = useState(''); is to keep the value which user is entering in the input field
const [{city, latitude, longitude}, dispatch] = useStateValue(); allows to access data from global state. There is dispatch is the method paired with the state, the dispatch will be passed to the call-back methods to update the state.

Adding WeatherInfo component

WeatherInfo component is to display the weather data.
Create a new file WeatherInfo.js under the src directory

import React from 'react';
import { useStateValue } from './store';

function WeatherInfo() {
    const [{weather}] = useStateValue();

    return weather && (
        <div className="weather-container">
            <div className="weather-icon">
              <img src={weather.iconId} alt={weather.description} />
              <div className="temprature-value">
                <p>{weather.temprature.value} *<span>C</span></p>
              </div>
              <div className="temprature-description">
                <p>{weather.description}</p>
              </div>
              <div className="location">
                <p>{weather.city}, {weather.country}</p>
              </div>
            </div>          
        </div>
    )
}

export default WeatherInfo;

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const [{weather}] = useStateValue(); allows to access the weather data from the global state.

Update the App.js

Now we have all the components, we will add them to our main app component

import React, { useEffect } from 'react';
import './App.css';
import { useStateValue } from './store';
import Notification from './Notification';
import WeatherInfo from './WeatherInfo';
import CityInfo from './CityInfo';
import { getWeather, KEY, updateWeather } from './reducers';

function App() {
  const [{error}, dispatch] = useStateValue();  

  useEffect(() => {     
    if ("geolocation" in navigator) {
      navigator.geolocation.getCurrentPosition((position) => {  
        let payload = {
          latitude: position.coords.latitude,
          longitude: position.coords.longitude
        };
        dispatch({
          type: "SET_LOCATION",
          payload
        });
        let api = `http://api.openweathermap.org/data/2.5/weather?lat=${payload.latitude}&lon=${payload.longitude}&appid=${KEY}`;
        getWeather(api)
        .then((data) => {
          updateWeather(dispatch, data);          
        })
        .catch (e => {            
            dispatch({
              type: "SET_ERROR",
              payload: {
                error: e
              }
            });
        });                   
      }, (error) => {  
        dispatch({
          type: "SET_ERROR",
          payload: {
            error
          }
        });              
      });
    }
  }, []);  

  return (    
    <div className="app">      
      <CityInfo />
      {error && <Notification />}
      {!error && <WeatherInfo />}
    </div>
  );
}

export default App;
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  • navigator.geolocation.getCurrentPosition allows to gets the current position of the user, this will prompt the message when launch for accessing the location.
  • {error && <Notification />} renders if there is an error.
  • {!error && <WeatherInfo />} renders if there is no error

Congrats!!!

Congrats!!! You have completed building the weather application from start to end.

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