Developed By
Gautam Kumar - Full stack developer
DEEP DIVE INTO
A "pan or drag" gesture in JavaScript refers to the action of moving an object or view by dragging it with a single touch point or mouse pointer.
This interaction is commonly used in web and mobile applications for tasks like scrolling content, rearranging elements, and moving objects within a canvas.
To implement "pan or drag" gestures, you'll need to track the touch or mouse movements and update the position of the dragged element accordingly.
Create variables to store the initial touch or mouse position, the current touch or mouse position, and a flag to indicate if a drag gesture is in progress.
javascriptvar initialX = 0;
var initialY = 0;
var isDragging = false;
Add an event listener for the touchstart
event (for touch devices) or the mousedown
event (for desktop browsers) to detect when a touch or mouse click occurs.
In the event handler, capture the initial position of the touch or mouse click and set the isDragging
flag to true
.
javascriptelement.addEventListener("touchstart", function(event) {
initialX = event.touches[0].pageX;
initialY = event.touches[0].pageY;
isDragging = true;
});
element.addEventListener("mousedown", function(event) {
initialX = event.pageX;
initialY = event.pageY;
isDragging = true;
});
Add an event listener for the touchmove
event (for touch devices) or the mousemove
event (for desktop browsers) to track the movement of the touch or mouse while a drag gesture is in progress.
In the event handler, continue checking if a drag gesture is ongoing.
Calculate the current position of the touch or mouse.
Determine the change in position (deltaX
and deltaY
) by subtracting the initial position from the current position.
Use the change in position to update the position of the dragged element.
javascriptelement.addEventListener("touchmove", function(event) {
if (!isDragging) return; // Ignore if not dragging
var currentX = event.touches[0].pageX;
var currentY = event.touches[0].pageY;
var deltaX = currentX - initialX;
var deltaY = currentY - initialY;
// Update the element's position based on deltaX and deltaY
// For example, you can use CSS `transform` or change the `left` and `top` properties.
element.style.transform = `translate(${deltaX}px, ${deltaY}px)`;
});
element.addEventListener("mousemove", function(event) {
if (!isDragging) return; // Ignore if not dragging
var currentX = event.pageX;
var currentY = event.pageY;
var deltaX = currentX - initialX;
var deltaY = currentY - initialY;
// Update the element's position based on deltaX and deltaY
// For example, you can use CSS `transform` or change the `left` and `top` properties.
element.style.transform = `translate(${deltaX}px, ${deltaY}px)`;
});
Add an event listener for the touchend
event (for touch devices) or the mouseup
event (for desktop browsers) to reset the isDragging
flag when the touch or mouse release occurs, indicating the end of the drag gesture.
javascriptelement.addEventListener("touchend", function(event) {
isDragging = false; // Reset the drag state
});
element.addEventListener("mouseup", function(event) {
isDragging = false; // Reset the drag state
});
By implementing the pan or drag gesture as described above, you can allow users to interact with draggable elements in your web or mobile applications. You can adapt this basic approach to suit your specific use case, including implementing constraints, bounds, and other functionality as needed.