如何确定onmousemove事件的方向？

Question

在某些情况下,我想onmousemove在鼠标停机时取消事件,例如.是否有可能确定onmousemove事件的方向？jQ或JS是好的.

我有拖拽元素.用户拖动元素.例如,如果元素的底部到达文档中的某个位置(即500px从文档的顶部),则onmousemove停止.如果用户将尝试再次向上拖动元素,则该功能将无法启动.只能向下拖动此元素.所以我认为通过捕捉mousemove事件的方向来做这件事很容易.但似乎没有这种标准属性.

Answer 1

您可以保存最后一个mousemove事件的位置以与当前位置进行比较:

//setup a variable to store our last position
var last_position = {},
$output       = $('#output');

//note that `.on()` is new in jQuery 1.7 and is the same as `.bind()` in this case
$(document).on('mousemove', function (event) {

    //check to make sure there is data to compare against
    if (typeof(last_position.x) != 'undefined') {

        //get the change from last position to this position
        var deltaX = last_position.x - event.clientX,
            deltaY = last_position.y - event.clientY;

        //check which direction had the highest amplitude and then figure out direction by checking if the value is greater or less than zero
        if (Math.abs(deltaX) > Math.abs(deltaY) && deltaX > 0) {
            //left
        } else if (Math.abs(deltaX) > Math.abs(deltaY) && deltaX < 0) {
            //right
        } else if (Math.abs(deltaY) > Math.abs(deltaX) && deltaY > 0) {
            //up
        } else if (Math.abs(deltaY) > Math.abs(deltaX) && deltaY < 0) {
            //down
        }
    }

    //set the new last position to the current for next time
    last_position = {
        x : event.clientX,
        y : event.clientY
    };
});

这是一个演示:http://jsfiddle.net/Dv29e/

更新

您还可以限制mousemove事件以获得鼠标移动的更多概念:

var last_position = {},
    $output       = $('#output'),
    mousemove_ok  = true,
    mouse_timer   = setInterval(function () {
        mousemove_ok = true;
    }, 500);
$(document).on('mousemove', function (event) {
    if (mousemove_ok) {
        mousemove_ok = false;
        ...
    }
});

如果符合以下条件,则仅检查光标在其过去位置的位置:

1. 最后一个位置存在.
2. 该mousemove_ok变量被设置为true它做每半秒.

这是一个受限制的演示:http://jsfiddle.net/Dv29e/4/

Answer 2

有一些标准属性显示与之前鼠标移动事件相关的增量:

document.addEventListener('mousemove', function (event) {
  directionX = event.movementX || event.mozMovementX || event.webkitMovementX || 0;
  directionY = event.movementY || event.mozMovementY || event.webkitMovementY || 0;
});

如文档中所述:

MouseEvent.movementX只读属性提供该事件与上一个mousemove事件之间鼠标指针的X坐标的移位.