How to use javascript to achieve the effect of mouse box

Mouse box is a common interactive effect that is widely used in web design and development. Using javascript to implement mouse boxes can not only enhance user experience, but also add more interactive effects to web pages. In this article, we will introduce how to use javascript to achieve the effect of the mouse box, and introduce the implementation methods and techniques in detail.

1. Use native javascript to realize the mouse box effect

Using native javascript to realize the mouse box requires two key steps: the operation when the mouse is pressed and the operation when the mouse is moved.

1. Mouse down event

When the mouse is pressed on an element, we need to trigger the corresponding event. This event is usually the mousedown event. In the mousedown event, we need to record the position of the mouse on the element so that we can later calculate the mouse movement distance.

// 获取鼠标按下时的位置
document.addEventListener('mousedown', e => {
  startX = e.pageX
  startY = e.pageY
  // 记录框选状态
  isSelecting = true
})

2. Mouse movement event

The position of the mouse on the element is recorded in the mouse press event. We need to calculate the distance of the mouse movement in the mouse movement event. And calculate the size and position of the mouse box based on the distance moved by the mouse. In the mouse movement event, we need to determine whether the mouse has been pressed. If not, there is no need to perform a frame selection.

// 鼠标移动事件
document.addEventListener('mousemove', e => {
  if (!isSelecting) return
  // 获取当前鼠标位置
  currentX = e.pageX
  currentY = e.pageY
  // 计算选框的宽高和位置
  selectBox.style.width = Math.abs(currentX - startX) + 'px'
  selectBox.style.height = Math.abs(currentY - startY) + 'px'
  selectBox.style.left = startX + (currentX > startX ? 0 : currentX - startX) + 'px'
  selectBox.style.top = startY + (currentY > startY ? 0 : currentY - startY) + 'px'
})

2. Mouse raised event

In the mouse raised event, we need to restore the box selection state to the default value.

// 鼠标抬起事件
document.addEventListener('mouseup', () => {
  isSelecting = false
})

2. Use jQuery to achieve the mouse box effect

jQuery is a popular javascript library. By using jQuery, we can achieve the mouse box effect more conveniently.

1. Mouse down event

In jQuery, we can use the mousedown event to listen for the mouse down event, and use event.pageX and event.pageY to get the mouse Location.

// 鼠标按下事件
$(document).on('mousedown', function(e) {
  startX = e.pageX
  startY = e.pageY
  // 记录框选状态
  isSelecting = true
})

2. Mouse move event

In jQuery, we can use the mousemove event to listen for the mouse move event, and use event.pageX and event.pageY to get the current mouse Location. Using jQuery, we can set the position and size of the selection box more conveniently.

// 鼠标移动事件
$(document).on('mousemove', function(e) {
  if (!isSelecting) return
  // 获取当前鼠标位置
  currentX = e.pageX
  currentY = e.pageY
  // 计算选框的宽高和位置
  selectBox.css({
    width: Math.abs(currentX - startX),
    height: Math.abs(currentY - startY),
    left: startX + (currentX > startX ? 0 : currentX - startX),
    top: startY + (currentY > startY ? 0 : currentY - startY)
  })
})

3. Mouse up event

In jQuery, we can use the mouseup event to listen for the mouse up event and restore the box selection state to the default value.

// 鼠标抬起事件
$(document).on('mouseup', function() {
  isSelecting = false
})

3. Tips and precautions

1. The position of the mouse pressed and the position of the mouse moved

Recording the position and calculation of the mouse pressed When measuring the distance that the mouse moves, we need to note that the position where the mouse is pressed and the position where the mouse moves are relative to the position of the current element. If the mouse moves outside the element, the calculated position needs to be limited to the inside of the element.

2. Mouse movement speed

When the mouse movement speed is fast, the frame selection effect may not be smooth enough. To solve this problem, we can use the requestAnimationFrame method, which can help us coordinate the speed and animation of mouse movement to achieve a smoother effect.

3. Frame selection order

When implementing the mouse frame effect, we need to pay attention to the frame selection order. If the order of frame selection is inconsistent, the effect of frame selection will produce errors. In order to avoid this situation, we can make some judgments on the distance the mouse has moved and determine the direction of the mouse movement.

In general, using JavaScript to implement mouse boxes is an effective way to enhance user experience. It can not only provide more interactive effects, but also add more functions to web pages. During the implementation process, you need to pay attention to issues such as the order of frame selection, mouse movement speed, and mouse movement position to ensure that the effect is smoother and more accurate.

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