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HTML 

              
                <html>
<head>
  <title>Flexbox Playground</title>
  <link href='https://fonts.googleapis.com/css?family=Varela+Round' rel='stylesheet' type='text/css'>
</head>
<body>
  <header class="header">
    <h2>Flexbox Playground by Marco Heine</h2>
    <p>This small demo shows the different Flexbox properties.<br> Use the following Options to see them in action.</p>
  </header>
  <div class="menu">
  <h2>Flexbox Container</h2>
    <div class="flexbox-container__select">
      <div>
        <label for="Display">Display</label><br>
        <select name="Display">
          <option value="flex">flex</option>
          <option value="inline-flex">inline-flex</option>
        </select>
      </div>
      <div>
        <label for="Flex-Direction">Flex-Direction</label><br>
        <select name="Display">
          <option value="column">column</option>
          <option value="row">row</option>
        </select>
      </div>
      <div>
        <label for="justify-content">Justify-Content</label><br>
        <select name="Justify-Content">
          <option value="flext-start">flex-start</option>
          <option value="flex-end">flex-end</option>
          <option value="center">center</option>
          <option value="space-between">space-between</option>
          <option value="space-around">space-around</option>
        </select>
      </div>
    </div>
  </div>
  <div class="container container-flex">
    <div class="item-1 item">Item 1</div>
    <div class="item-2 item">Item 2</div>
    <div class="item-3 item">Item 3</div>
    <div class="item-4 item">Item 4</div>
    <div class="item-5 item">Item 5</div>
    <div class="item-6 item">Item 6</div>
  </div>
</body>
</html>
!

CSS 

              
                /* ================================= 
  General Styles
==================================== */

* {
  box-sizing: border-box;
}

body {
  background: #e8e9e9;
  color: #fff;
  font-size: 1.35em;
  font-family: 'Varela', sans-serif;
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 5%;
}

.header,
.menu {
  background: #fff;
  border-radius: 5px;
  color: #000;
  margin: 45px auto;
  padding: 5px 0 30px 0;
  text-align: center;
}

label {
  font-size: 18px;
}

.flexbox-container__select {
  display: flex;
  justify-content: space-around;
}

.container {
  background: #fff;
  border-radius: 5px;
  margin: 45px auto;
  padding: 10px;
}

.item {
  background: #3db5da;
  border-radius: 5px;
  color: #fff;
  margin: 5px;
  padding: 15px;
}

/* ================================= 
  Flexbox Styles
==================================== */

.container-flex {
  display: flex;
  flex-direction: column;
}
!

JS 

              
                //Select the Flexbox Container
var container = document.getElementsByClassName('container')[0];
//Select the select menu for the Display Property
var selectDisplay = document.getElementsByTagName('select')[0];
//Select the select menu for the Flex-Direction Property
var selectFlexDirection = document.getElementsByTagName('select')[1];
//Select the select menu for the justify-content Property
var selectJustifyContent = document.getElementsByTagName('select')[2];
//When another option from the select menu is chosen, call the function to change it's CSS property
selectDisplay.addEventListener('change', displayChanger, false);
selectFlexDirection.addEventListener('change', directionChanger, false);
selectJustifyContent.addEventListener('change', justifyContentChanger, false);



function displayChanger() {
  //Select the option's text from the select menu
  var selectedOptionText = selectDisplay.options[selectDisplay.selectedIndex].text;
  //Check the chosen select option
  if (selectedOptionText === 'inline-flex') {
    console.log(selectedOptionText);
    //Change the CSS property according to the chosen select option
    container.style.display = 'inline-flex';
  }
  else {
    console.log(selectedOptionText);
    container.style.display = 'flex';
  } 
}

function directionChanger() {
  var selectedOptionText = selectFlexDirection.options[selectFlexDirection.selectedIndex].text;
  if (selectedOptionText === 'row') {
    console.log(selectedOptionText);
    container.style.flexDirection = 'row';
  }
  else {
    console.log(selectedOptionText);
    container.style.flexDirection = 'column';
  } 
}

function justifyContentChanger() {
  var selectedOptionText = selectJustifyContent.options[selectJustifyContent.selectedIndex].text;
  if (selectedOptionText === 'flex-end') {
    console.log(selectedOptionText);
    container.style.justifyContent = 'flex-end';
  }
  else if (selectedOptionText === 'flex-start') {
    console.log(selectedOptionText);
    container.style.justifyContent = 'flex-start';
  } 
  else if (selectedOptionText === 'center') {
    console.log(selectedOptionText);
    container.style.justifyContent = 'center';
  }
  else if (selectedOptionText === 'space-between') {
    console.log(selectedOptionText);
    container.style.justifyContent = 'space-between';
  }
  else {
    console.log(selectedOptionText);
    container.style.justifyContent = 'space-around';
  }
}
!
999px

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