<section class="top-banner">
  <div class="container">
    <h1 class="heading">Simple Weather App</h1>
    <form>
      <input type="text" placeholder="Search for a city" autofocus>
      <button type="submit">SUBMIT</button>
      <span class="msg"></span>
    </form>
  </div>
</section>
<section class="ajax-section">
  <div class="container">
    <ul class="cities"></ul>
  </div>
</section>
<footer class="page-footer">
  <div class="container">
    <small>Made with <span>❤</span> by <a href="http://georgemartsoukos.com/" target="_blank">George Martsoukos</a>
    </small>
  </div>
</footer>
/* RESET STYLES
–––––––––––––––––––––––––––––––––––––––––––––––––– */
:root {
  --bg_main: #0a1f44;
  --text_light: #fff;
  --text_med: #53627c;
  --text_dark: #1e2432;
  --red: #ff1e42;
  --darkred: #c3112d;
  --orange: #ff8c00;
}

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  font-weight: normal;
}

a {
  color: inherit;
  text-decoration: none;
}

button {
  cursor: pointer;
}
 
input {
  -webkit-appearance: none;
}
 
button,
input {
  border: none;
  background: none;
  outline: none;
  color: inherit;
}

img {
  display: block;
  max-width: 100%;
  height: auto;
}

ul {
  list-style: none;
}

body {
  font: 1rem/1.3 "Roboto", sans-serif;
  background: var(--bg_main);
  color: var(--text_dark);
  padding: 50px;
}

.container {
  width: 100%;
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 15px;
}


/* SECTION #1
–––––––––––––––––––––––––––––––––––––––––––––––––– */
.top-banner {
  color: var(--text_light);
}

.heading {
  font-weight: bold;
  font-size: 4rem;
  letter-spacing: 0.02em;
  padding: 0 0 30px 0;
}

.top-banner form {
  position: relative;
  display: flex;
  align-items: center;
}

.top-banner form input {
  font-size: 2rem;
  height: 40px;
  padding: 5px 5px 10px;
  border-bottom: 1px solid;
}

.top-banner form input::placeholder {
  color: currentColor; 
}

.top-banner form button {
  font-size: 1rem;
  font-weight: bold;
  letter-spacing: 0.1em;
  padding: 15px 20px;
  margin-left: 15px;
  border-radius: 5px;
  background: var(--red);
  transition: background 0.3s ease-in-out;
}

.top-banner form button:hover {
  background: var(--darkred);
}

.top-banner form .msg {
  position: absolute;
  bottom: -40px;
  left: 0;
  max-width: 450px;
  min-height: 40px;
}


/* SECTION #2
–––––––––––––––––––––––––––––––––––––––––––––––––– */
.ajax-section {
  margin: 70px 0 20px;
}

.ajax-section .cities {
  display: grid;
  grid-gap: 32px 20px;
  grid-template-columns: repeat(4, 1fr);
}

.ajax-section .city {
  position: relative;
  padding: 40px 10%;
  border-radius: 20px;
  background: var(--text_light);
  color: var(--text_med);
}

.ajax-section .city::after {
  content: '';
  width: 90%;
  height: 50px;
  position: absolute;
  bottom: -12px;
  left: 5%;
  z-index: -1;
  opacity: 0.3;
  border-radius: 20px;
  background: var(--text_light);
}

.ajax-section figcaption {
  margin-top: 10px;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.ajax-section .city-temp {
  font-size: 5rem;
  font-weight: bold;
  margin-top: 10px;
  color: var(--text_dark);
}

.ajax-section .city sup {
  font-size: 0.5em;
}

.ajax-section .city-name sup {
  padding: 0.2em 0.6em;
  border-radius: 30px;
  color: var(--text_light);
  background: var(--orange);
}

.ajax-section .city-icon {
  margin-top: 10px;
  width: 100px;
  height: 100px;
}


/* FOOTER
–––––––––––––––––––––––––––––––––––––––––––––––––– */
.page-footer {
  text-align: right;
  font-size: 1rem;
  color: var(--text_light);
  margin-top: 40px;
}

.page-footer span {
  color: var(--red);
}


/* MQ
–––––––––––––––––––––––––––––––––––––––––––––––––– */
@media screen and (max-width: 1000px) {
  body {
    padding: 30px;
  }
  
  .ajax-section .cities {
    grid-template-columns: repeat(3, 1fr);
  }
}

@media screen and (max-width: 700px) {
  .heading,
  .ajax-section .city-temp {
    font-size: 3rem;
  }
  
  .ajax-section {
    margin-top: 20px;
  }
  
  .top-banner form {
    flex-direction: column;
    align-items: flex-start;
  }
  
  .top-banner form input,
  .top-banner form button {
    width: 100%;
  }

  .top-banner form button {
    margin: 20px 0 0 0;
  }
  
  .top-banner form .msg {
    position: static;
    max-width: none;
    min-height: 0;
    margin-top: 10px;
  }

  .ajax-section .cities {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media screen and (max-width: 500px) {
  body {
    padding: 15px;
  }
  
  .ajax-section .cities {
    grid-template-columns: repeat(1, 1fr);
  }
}
/*SEARCH BY USING A CITY NAME (e.g. athens) OR A COMMA-SEPARATED CITY NAME ALONG WITH THE COUNTRY CODE (e.g. athens,gr)*/
const form = document.querySelector(".top-banner form");
const input = document.querySelector(".top-banner input");
const msg = document.querySelector(".top-banner .msg");
const list = document.querySelector(".ajax-section .cities");
/*PUT YOUR OWN KEY HERE - THIS MIGHT NOT WORK
SUBSCRIBE HERE: https://home.openweathermap.org/users/sign_up*/
const apiKey = "4d8fb5b93d4af21d66a2948710284366";

form.addEventListener("submit", e => {
  e.preventDefault();
  let inputVal = input.value;

  //check if there's already a city
  const listItems = list.querySelectorAll(".ajax-section .city");
  const listItemsArray = Array.from(listItems);

  if (listItemsArray.length > 0) {
    const filteredArray = listItemsArray.filter(el => {
      let content = "";
      //athens,gr
      if (inputVal.includes(",")) {
        //athens,grrrrrr->invalid country code, so we keep only the first part of inputVal
        if (inputVal.split(",")[1].length > 2) {
          inputVal = inputVal.split(",")[0];
          content = el
            .querySelector(".city-name span")
            .textContent.toLowerCase();
        } else {
          content = el.querySelector(".city-name").dataset.name.toLowerCase();
        }
      } else {
        //athens
        content = el.querySelector(".city-name span").textContent.toLowerCase();
      }
      return content == inputVal.toLowerCase();
    });

    if (filteredArray.length > 0) {
      msg.textContent = `You already know the weather for ${
        filteredArray[0].querySelector(".city-name span").textContent
      } ...otherwise be more specific by providing the country code as well 😉`;
      form.reset();
      input.focus();
      return;
    }
  }

  //ajax here
  const url = `https://api.openweathermap.org/data/2.5/weather?q=${inputVal}&appid=${apiKey}&units=metric`;

  fetch(url)
    .then(response => response.json())
    .then(data => {
      const { main, name, sys, weather } = data;
      const icon = `https://s3-us-west-2.amazonaws.com/s.cdpn.io/162656/${
        weather[0]["icon"]
      }.svg`;

      const li = document.createElement("li");
      li.classList.add("city");
      const markup = `
        <h2 class="city-name" data-name="${name},${sys.country}">
          <span>${name}</span>
          <sup>${sys.country}</sup>
        </h2>
        <div class="city-temp">${Math.round(main.temp)}<sup>°C</sup></div>
        <figure>
          <img class="city-icon" src="${icon}" alt="${
        weather[0]["description"]
      }">
          <figcaption>${weather[0]["description"]}</figcaption>
        </figure>
      `;
      li.innerHTML = markup;
      list.appendChild(li);
    })
    .catch(() => {
      msg.textContent = "Please search for a valid city 😩";
    });

  msg.textContent = "";
  form.reset();
  input.focus();
});

External CSS

  1. https://fonts.googleapis.com/css?family=Roboto:300,400,700&amp;display=swap

External JavaScript

This Pen doesn't use any external JavaScript resources.