Resizable div JavaScript Code with Example

This tutorial will guide you through the process of creating a resizable div using Javascript. This is a useful feature for web applications that require flexible layouts, allowing users to adjust the size of elements dynamically for a more personalized experience. By implementing this resizable div Javascript code with example, you can enhance user interaction and improve the overall usability of your web interfaces.

How to Create a Resizable Div

Step 1: HTML Structure

First, we need to create the basic HTML structure for our resizable div. This includes the main div and smaller divs that act as resizers, positioned at each corner.

<div class='resizable'>
  <div class='resizers'>
    <div class='resizer top-left'></div>
    <div class='resizer top-right'></div>
    <div class='resizer bottom-left'></div>
    <div class='resizer bottom-right'></div>
  </div>
</div>
    <script  src="./script.js"></script>

Step 2: CSS Styling

Next, we’ll apply CSS styles to visually define the resizable div and its resizers. This includes setting the background color, size, border, and positioning of the resizers.

body,
html {
  background: black;
}
.resizable {
  background: white;
  width: 100px;
  height: 100px;
  position: absolute;
  top: 100px;
  left: 100px;
}

.resizable .resizers{
  width: 100%;
  height: 100%;
  border: 3px solid #4286f4;
  box-sizing: border-box;
}

.resizable .resizers .resizer{
  width: 10px;
  height: 10px;
  border-radius: 50%; /*magic to turn square into circle*/
  background: white;
  border: 3px solid #4286f4;
  position: absolute;
}

.resizable .resizers .resizer.top-left {
  left: -5px;
  top: -5px;
  cursor: nwse-resize; /*resizer cursor*/
}
.resizable .resizers .resizer.top-right {
  right: -5px;
  top: -5px;
  cursor: nesw-resize;
}
.resizable .resizers .resizer.bottom-left {
  left: -5px;
  bottom: -5px;
  cursor: nesw-resize;
}
.resizable .resizers .resizer.bottom-right {
  right: -5px;
  bottom: -5px;
  cursor: nwse-resize;
}

Step 3: JavaScript Functionality

Now, we’ll add the JavaScript code that enables the resizing functionality. This code captures mouse events on the resizers and updates the div’s dimensions accordingly.

/*Make resizable div by Hung Nguyen*/
function makeResizableDiv(div) {
  const element = document.querySelector(div);
  const resizers = document.querySelectorAll(div + ' .resizer')
  const minimum_size = 20;
  let original_width = 0;
  let original_height = 0;
  let original_x = 0;
  let original_y = 0;
  let original_mouse_x = 0;
  let original_mouse_y = 0;
  for (let i = 0;i < resizers.length; i++) {
    const currentResizer = resizers[i];
    currentResizer.addEventListener('mousedown', function(e) {
      e.preventDefault()
      original_width = parseFloat(getComputedStyle(element, null).getPropertyValue('width').replace('px', ''));
      original_height = parseFloat(getComputedStyle(element, null).getPropertyValue('height').replace('px', ''));
      original_x = element.getBoundingClientRect().left;
      original_y = element.getBoundingClientRect().top;
      original_mouse_x = e.pageX;
      original_mouse_y = e.pageY;
      window.addEventListener('mousemove', resize)
      window.addEventListener('mouseup', stopResize)
    })
    
    function resize(e) {
      if (currentResizer.classList.contains('bottom-right')) {
        const width = original_width + (e.pageX - original_mouse_x);
        const height = original_height + (e.pageY - original_mouse_y)
        if (width > minimum_size) {
          element.style.width = width + 'px'
        }
        if (height > minimum_size) {
          element.style.height = height + 'px'
        }
      }
      else if (currentResizer.classList.contains('bottom-left')) {
        const height = original_height + (e.pageY - original_mouse_y)
        const width = original_width - (e.pageX - original_mouse_x)
        if (height > minimum_size) {
          element.style.height = height + 'px'
        }
        if (width > minimum_size) {
          element.style.width = width + 'px'
          element.style.left = original_x + (e.pageX - original_mouse_x) + 'px'
        }
      }
      else if (currentResizer.classList.contains('top-right')) {
        const width = original_width + (e.pageX - original_mouse_x)
        const height = original_height - (e.pageY - original_mouse_y)
        if (width > minimum_size) {
          element.style.width = width + 'px'
        }
        if (height > minimum_size) {
          element.style.height = height + 'px'
          element.style.top = original_y + (e.pageY - original_mouse_y) + 'px'
        }
      }
      else {
        const width = original_width - (e.pageX - original_mouse_x)
        const height = original_height - (e.pageY - original_mouse_y)
        if (width > minimum_size) {
          element.style.width = width + 'px'
          element.style.left = original_x + (e.pageX - original_mouse_x) + 'px'
        }
        if (height > minimum_size) {
          element.style.height = height + 'px'
          element.style.top = original_y + (e.pageY - original_mouse_y) + 'px'
        }
      }
    }
    
    function stopResize() {
      window.removeEventListener('mousemove', resize)
    }
  }
}

makeResizableDiv('.resizable')

Step 4: Header Assets (Optional)

If you need to include external libraries or stylesheets, place their CDN links here. This is where you would add any necessary dependencies for your project.

Step 5: Footer Assets (Optional)

If you need to include external Javascript files , place their CDN links here.

That’s it! You’ve successfully created a resizable div using Javascript. This example provides a foundation for implementing resizable elements in your web projects. Remember to customize the styles and functionality to fit your specific requirements.