Simple Plain WYSIWYG Editor with JavaScript and CSS

A basic WYSIWYG rich text editor that built with plain HTML, CSS and a little JavaScript.

How to use it:

The html structure for the WYSIWYG editor.

<div id="textarea">
  <div id="control_p" class='controls'>
    <button class="boldify">B</button>
    <button class="italify">I</button>
    <button class="underline">U</button>
    <button class="font_size">Size</button>
    <button class="font_color">Color</button>
    <button class="create_link">Link</button>
    <button class="add_image">Image</button>
    <button class="insert_ul">UL</button>
    <button class="insert_ol">OL</button>
    <button class="insert_horizontal">Line</button>
  </div>
  <iframe name="textarea" class="rich_text"></iframe>
</div>

The required CSS styles.

#textarea {
  width: 900px;
  margin: 30px auto;
  position: absolute;
  left: 50%;
  -webkit-transform: translateX(-50%);
  -ms-transform: translateX(-50%);
  transform: translateX(-50%);
  box-shadow: 0 0 10px 5px rgba(0, 0, 0, 0.3);
  background-color: #555;
  padding: 5px 20px 20px;
}
#textarea .controls {
  width: 100%;
  padding: 15px 0 10px;
  display: -webkit-box;
  display: -webkit-flex;
  display: -ms-flexbox;
  display: flex;
  -webkit-box-orient: horizontal;
  -webkit-box-direction: normal;
  -webkit-flex-direction: row;
  -ms-flex-direction: row;
  flex-direction: row;
}
#textarea .controls button {
  -webkit-box-flex: 1;
  -webkit-flex-grow: 1;
  -ms-flex-positive: 1;
  flex-grow: 1;
  outline: none;
  border: none;
  background-color: #F44336;
  color: #fff;
  padding: 10px 10px;
  margin: 0 1px;
  cursor: pointer;
  -webkit-transition: all 0.3s ease-in-out;
  transition: all 0.3s ease-in-out;
  box-shadow: 0 0 1px 1px rgba(0, 0, 0, 0.3);
}
#textarea .controls button:hover { box-shadow: 0 0 10px 1px rgba(0, 0, 0, 0.7); }
#textarea .rich_text {
  background-color: #fff;
  border: none;
  width: 100%;
  min-height: 200px;
  padding: 20px;
  cursor: text;
}

The core JavaScript to enable the WYSIWYG editor.

(function() {
  var textarea_elem = textarea.document;
  var boldify = function() {
    textarea_elem.execCommand('bold', false, null);
  };
  var italify = function() {
    textarea_elem.execCommand('italic', false, null);
  };
  var underline = function() {
    textarea_elem.execCommand('underline', false, null);
  };
  var font_size = function() {
    var size = prompt('Font-size (1 to 7)', '');
    textarea_elem.execCommand('FontSize', false, size);
  };
  var font_color = function() {
    var color = prompt('FontColor (enter either color name or hex or rgb or hsl) :', '');
    textarea_elem.execCommand('ForeColor', false, color);
  };
  var create_link = function() {
    var linkURL = prompt("URL for the link:", "http://");
    textarea_elem.execCommand("CreateLink", false, linkURL);
  };
  var add_image = function() {
    var imgSrc = prompt('Enter image address', '');
    if (imgSrc !== null) {
      textarea_elem.execCommand('insertimage', false, imgSrc);
    }
  };
  var insert_horizontal = function() {
    textarea_elem.execCommand('inserthorizontalrule', false, null);
  };
  var insert_ol = function() {
    textarea_elem.execCommand("InsertOrderedList", false, "newOL");
  };
  var insert_ul = function() {
    textarea_elem.execCommand("InsertUnorderedList", false, "newUL");
  };
  window.onload = function() {
    textarea_elem.designMode = 'On';
    document.querySelector('.boldify').addEventListener('click', boldify);
    document.querySelector('.italify').addEventListener('click', italify);
    document.querySelector('.underline').addEventListener('click', underline);
    document.querySelector('.font_size').addEventListener('click', font_size);
    document.querySelector('.font_color').addEventListener('click', font_color);
    document.querySelector('.create_link').addEventListener('click', create_link);
    document.querySelector('.add_image').addEventListener('click', add_image);
    document.querySelector('.insert_horizontal').addEventListener('click', insert_horizontal);
    document.querySelector('.insert_ol').addEventListener('click', insert_ol);
    document.querySelector('.insert_ul').addEventListener('click', insert_ul);
  };
})();
)