CSS > calculadora rem a px

by academiax

HTML

<div class="container">
  <div class="input-container">
    <input id="font-size-input" type="number" step="any" value="16">
    <label for="font-size-input">Tamaño de fuente en la raíz</label>
  </div>
</div>
<div class="container">
  <div class="input-container">
    <input id="rem-input" type="number" step="any">
    <label for="rem-input">Rem</label>
  </div>
  <div class="input-container">
    <input id="px-input" type="number" step="any">
    <label for="px-input">Px</label>
  </div>
</div>

CSS

body {
  margin: 40px;
}
* {
  box-sizing: border-box;
}

body {
  background-color: #111;
  color: white;
  font-family: "Montserrat", sans-serif;
  font-size: 16px;
}

.container {
  display: flex;
  flex-wrap: wrap;
  margin-bottom: 30px;
}

.input-container {
  position: relative;
  margin-right: 20px;
  margin-bottom: 20px;
  flex: 1 0 200px;
}

.input-container label {
  position: absolute;
  top: 10px;
  left: 12px;
  font-size: 16px;
  color: #bbb;
  pointer-events: none;
  transition: all 0.2s ease-out;
}

.input-container input {
  width: 100%;
  padding: 15px 12px 5px;
  border: none;
  border-bottom: 2px solid #ccc;
  background-color: transparent;
  color: white;
  font-size: 24px;
  font-weight: 300;
}

.input-container input:focus + label,
.input-container input:not(:placeholder-shown) + label {
  top: -10px;
  font-size: 12px;
  color: #fff;
}

label {
  font-size: 16px;
  color: #bbb;
}

input[type="number"] {
  -moz-appearance: textfield;
}

input::-webkit-outer-spin-button,
input::-webkit-inner-spin-button {
  -webkit-appearance: none;
  margin: 0;
}

input[type="number"]:focus {
  outline: none;
}

input[type="number"]::-webkit-outer-spin-button,
input[type="number"]::-webkit-inner-spin-button {
  -webkit-appearance: none;
  margin: 0;
}

JavaScript

const remInput = document.getElementById('rem-input');
const pxInput = document.getElementById('px-input');
const fontSizeInput = document.getElementById('font-size-input');

function convertRemToPx() {
  const rem = parseFloat(remInput.value);
  const fontSize = parseFloat(fontSizeInput.value);
  const px = rem * fontSize;

  if (Number.isInteger(px)) {
    pxInput.value = Math.round(px);
  } else {
    pxInput.value = px.toFixed(2);
  }
  pxInput.style.borderColor = "blue";
  setTimeout(function() {
    pxInput.style.borderColor = "#ccc";
  }, 500);
}

function convertPxToRem() {
  const px = parseFloat(pxInput.value);
  const fontSize = parseFloat(fontSizeInput.value);
  const rem = px / fontSize;

  if (Number.isInteger(rem)) {
    remInput.value = Math.round(rem);
  } else {
    remInput.value = rem.toFixed(2);
  }
  remInput.style.borderColor = "blue";
  setTimeout(function() {
    remInput.style.borderColor = "#ccc";
  }, 500);
}

remInput.addEventListener('input', convertRemToPx);
pxInput.addEventListener('input', convertPxToRem);
fontSizeInput.addEventListener('input', function() {
  convertRemToPx();
  convertPxToRem();
});