<form name="bmiForm">
<div class="bmi-calculator">
  <h1 style="margin-bottom: 1em;">Izračunaj svoj ITM</h1>
  <div class="bmi-calculator-weight">
    <input class="weight-slider" name="realweight" id="myWeight" type="range" min="25" max="180" value="60"/>
    <p style="margin-top: 1.8em;">
      TEŽA: 
      <input name="Teža" id="inputWeight" type="number" value="60" min="25" max="180" oninput="showValWeight(this.value)"/>
      <span id="weight"></span> kg
    </p>
  </div>
  <div class="bmi-calculator-height">
    <input class="height-slider" name="realheight" id="myHeight" type="range" min="100" max="230" value="160">
    <p style="margin-top: 1.8em;">
      VIŠINA:
      <input name="Višina" id="inputHeight" type="number" value="160" min="100" max="230" oninput="showValHeight(this.value)"/>
      <span id="height"></span> cm
    </p>
  </div>
  <input class="gumb" type="button" value="Izračunaj" onclick="calculateBmi()" style="margin-top: 0.5em">
 <p style="margin-top: 1em;font-size: 1.2em;">
   <strong>Tvoj ITM:</strong>
   <span id="yourbmi" style="font-size: 1.2em;margin-left: 8px;"></span>
 </p>
 <p></p>
 <p>
   <span id="evaluationMessage"></span>
 </p>
</div>
</form>
/* Import Roboto font from Google Fonts */
@import url('https://fonts.googleapis.com/css?family=Roboto:400,500,700&display=swap');
/*
  Define CSS variables for colors
*/
:root {
  --background-color: #f6f6f6;
  --vigo-color: #f09831;
  --slider-color: #A3A3A3;
  --input-number-color: #EBEBEB;
}
/* Prepare your work table. 😎 */
* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}
/* 
  Push sliders down from <h1> tag
*/
h1 {
  text-align: center;
  margin-left: 0.2em;
  margin-right: 0.2em;
  margin-bottom: 0.9em;
}
/* 
  Define positioning of the elements inside <body>
*/
html,
body {
  height: 100%; width: 100%;
  margin: 0; padding: 0;
  background-color: var(--background-color);
  color: black;
}

body {
  display: flex;
  justify-content: center;
  align-items: center;
  font-family: 'Roboto', sans-serif;
}
/*
  Styling for calculator <div>
*/
.bmi-calculator {
  border: 5px solid white;
  -moz-box-shadow: 0px 0px 5px hsl(15, 2%, 55%);
  -webkit-box-shadow: 0px 0px 5px hsl(15, 2%, 55%);
  box-shadow: 0px 0px 10px hsl(0,0%,73.9%);
  padding: 3em;
  margin: 2em;
  height: 520px;
  background-color: white;
}
/*
  Styling for div elements wrapping both sliders
*/
.bmi-calculator-weight, .bmi-calculator-height {
  /* Positioning */
  /*border: dotted 1px red;*/
  margin-bottom: 2.2em;
  width: 100%;
  /* background:
    repeating-linear-gradient(90deg, #c8c8c8, #c8c8c8 0.125em /* lines *//*, transparent 0.125em, transparent 1.25em /* space between 
      *//*) 80% no-repeat;
  /*background-size: 100% /* = 10*1.25em + .125em */ /*20%;*/
}
/*
  Styling for both sliders
*/
.weight-slider, .height-slider {
  width: 100%;
  height: 1px;
  border-radius: 10px;
  background: var(--slider-color); /* Light grey background. */
  outline: none; /* Remove outline. */
  /*opacity: 0.7; *//* Set transparency (for mouse-over effects on hover) */
  /*-webkit-transition: .2s;*/ /* 0.2 seconds transition on hover */
  /*transition: opacity .2s;*/
}

/* Mouse-over effects 🖱 računalniška miška */
/*.weight-slider:hover, .height-slider:hover *//*{
  opacity: 1; *//* Fully shown on mouse-over *//*
}*/


/* DEFINE STYLING FOR INPUT RANGE SLIDERS & INPUT TYPE NUMBER FOR BROWSER COMPATIBILITY
  https://css-tricks.com/styling-cross-browser-compatible-range-inputs-css/
*/
input[type=range] {
  -moz-appearance: none; /* Override default CSS styles */
  -webkit-appearance: none;
  appearance: none;
  cursor: pointer;
}

input[type=range]:focus {
  outline: none; /* Removes the blue border. You should probably do some kind of focus styling for accessibility reasons though. */
}
input[type=range]::-ms-track {
  width: 100%;
  cursor: pointer;
}

/* Special styling for WebKit/Blink */
input[type=range]::-webkit-slider-thumb {
  -webkit-appearance: none;
  border: 2.5px solid var(--vigo-color);
  height: 20px;
  width: 20px;
  border-radius: 40px;
  background: white;
  cursor: pointer;
  margin-top: 0px; /* You need to specify a margin in Chrome, but in Firefox and IE it is automatic */
  /* box-shadow: 1px 1px 1px #000000, 0px 0px 1px #0d0d0d; */ /* Add cool effects to your sliders! */
}

/* All the same stuff for Firefox */
input[type=range]::-moz-range-thumb {
  /* box-shadow: 1px 1px 1px #000000, 0px 0px 1px #0d0d0d; */
  border: 2.5px solid var(--vigo-color);
  height: 20px;
  width: 20px;
  border-radius: 40px;
  background: white;
  cursor: pointer;
}

/* All the same stuff for IE */
input[type=range]::-ms-thumb {
  /* box-shadow: 1px 1px 1px #000000, 0px 0px 1px #0d0d0d; */
  border: 2.5px solid var(--vigo-color);
  height: 20px;
  width: 20px;
  border-radius: 40px;
  background: white;
  cursor: pointer;
}

/* INPUT TYPE NUMBER STYLING*/
input[type=number] {
  -moz-appearance: none; /* Override default CSS styles */
  -webkit-appearance: none;
  cursor: pointer;
  /* Real styling part :D */
  background: var(--input-number-color);
  border-style: none;
  height: 30px;
  width: 60px;
  margin-left: 20px;
  margin-right: 10px;
  text-align: right;
  font-family: 'Roboto', sans-serif;
  font-size: 1.5em;
}

input[type=number]:focus {
  outline: none; /* Removes the blue border. You should probably do some kind of focus styling for accessibility reasons though. */
}

/*
  *** END OF DEFAULT STYLING VALUES FOR INPUT RANGE SLIDERS & INPUT TYPE NUMBER ***
*/

/*
  Styling for "Calculate" button
*/
.gumb {
  text-align: center;
  font-size: 1em;
  color: white;
  width: 100%;
  margin-bottom: 10px;
  padding: 11px 32px;
  border: none;
  background-color: var(--vigo-color);
  text-transform: uppercase;
  cursor: pointer;
}

/*
  Media querie for iPhone 5
*/
@media only screen and (max-width: 325px) {
  .bmi-calculator {
    height: 560px;
  }
  
  h1 {
    font-size: 1.5em;
  }
}
'use strict';
// Define variables for range sliders
// Weight variables
var weightSlider = document.getElementById("myWeight");
var weightOutput = document.getElementById("inputWeight");
// Height variables
var heightSlider = document.getElementById("myHeight");
var heightOutput = document.getElementById("inputHeight");
// Display slider value
weightOutput.innerHTML = weightSlider.value;
heightOutput.innerHTML = heightSlider.value;
// Update sliders in real time while dragging it
weightSlider.oninput = function () {
  weightOutput.innerHTML = this.value;
}
heightSlider.oninput = function () {
  heightOutput.innerHTML = this.value;
}
// Change weight-slider value on weight-number input
function showValWeight(newVal) {
  weightSlider.value=newVal;
};
// Change height-slider value on height-number input
function showValHeight(newVal) {
  heightSlider.value=newVal;
};
// *** Change number input when dragging slider ***
// Add 2 eventListeners for weight and input sliders
weightSlider.addEventListener("input", updateValueWeight);
heightSlider.addEventListener("input", updateValueHeight);
function updateValueWeight(e) {
  weightOutput.value = e.srcElement.value;
}
function updateValueHeight(e) {
  heightOutput.value = e.srcElement.value;
}
// Calculate BMI
function calculateBmi() {
  var weight = document.bmiForm.realweight.value;
  var height = (document.bmiForm.realheight.value)/100;
  var realbmi = (weight)/Math.pow(height, 2);
  var realbmiOutput = document.getElementById("yourbmi");
  var messageOutput = document.getElementById("evaluationMessage");
  var roundedBmi = realbmi.toFixed(1);
  messageOutput.innerHTML = ""; // Clear message before calculating new BMI
  realbmiOutput.innerHTML = " " + roundedBmi; // Print BMI
  // Appropriate message for your BMI rating
  //if (roundedBmi > 26) {
  //  messageOutput.innerHTML = "YOU'RE A FAT ASS!!!";
  // } else //{
  //}
  // Console loggings
  console.log('Teža: ' + weight + " kg");
  console.log('Višina: ' + height + " m");
  console.log('BMI: ' + realbmi);
}

External CSS

This Pen doesn't use any external CSS resources.

External JavaScript

  1. https://cdnjs.cloudflare.com/ajax/libs/jquery/3.4.1/jquery.min.js