Created
November 30, 2016 14:03
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Implementing mouse trail using requestAnimationFrame for EloquentJavaScript Exercise 14.2
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| <!doctype html> | |
| <style> | |
| .trail { /* className for the trail elements */ | |
| position: absolute; | |
| height: 6px; width: 6px; | |
| border-radius: 3px; | |
| background: teal; | |
| } | |
| body { | |
| height: 300px; | |
| } | |
| </style> | |
| <body> | |
| <script> | |
| var pointerX, pointerY; | |
| var lastX = null, lastY = null; | |
| var dots = []; | |
| for (var i = 0; i < 12; i++) { | |
| var node = document.createElement("div"); | |
| node.className = "trail"; | |
| node.setAttribute("targetTime", i + 1); | |
| document.body.appendChild(node); | |
| dots.push(node); | |
| } | |
| var currentDot = 0; | |
| addEventListener("mousemove", function(event) { | |
| pointerX = event.pageX; | |
| pointerY = event.pageY; | |
| }); | |
| var delta = 0, lastTime = null; | |
| function animate(time) { | |
| if (lastTime != null) | |
| delta = time - lastTime; | |
| lastTime = time; | |
| dots.forEach(function(dot) { | |
| var boundingObj = dot.getBoundingClientRect(); | |
| var currentX = boundingObj.left + 3; | |
| var currentY = boundingObj.top + 3; | |
| if (Math.abs(currentX - pointerX) < 1 && Math.abs(currentY - pointerY) < 1) { | |
| dot.style.left = pointerX - 3; | |
| dot.style.top = pointerY - 3; | |
| return; | |
| } | |
| var currentDistance = Math.sqrt((currentX - pointerX) * (currentX - pointerX) + | |
| (currentY - pointerY) * (currentY - pointerY)); | |
| if (pointerX != lastX || pointerY != lastY) { | |
| //targetTime is in second | |
| var v = currentDistance / (dot.getAttribute("targetTime") * 1000); | |
| dot.setAttribute("velocity", v); | |
| } | |
| var step = dot.getAttribute("velocity") * delta; | |
| //step * cos | |
| var stepX = step * ((pointerX - currentX) / currentDistance); | |
| dot.style.left = boundingObj.left + stepX + "px"; | |
| //step * sin | |
| var stepY = step * ((pointerY - currentY) / currentDistance); | |
| dot.style.top = boundingObj.top + stepY + "px"; | |
| }); | |
| lastX = pointerX; | |
| lastY = pointerY; | |
| requestAnimationFrame(animate); | |
| } | |
| requestAnimationFrame(animate); | |
| </script> | |
| </body> |
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