javascript - 在其他函数中只执行一次函数

Question

我有以下功能：

div_paper.onmousedown = function(event) {
    var mouseCoords = getCoords(event);
    startX = mouseCoords.x - offset[0];
    startY = mouseCoords.y - offset[1];
    rect = paper.rect(startX, startY, 0, 0);
    document.onmousemove = doDraw;
    // the function below i would like to fire once
    rect.drag(drag_move, drag_start, drag_up);
};

如您所见，它会在每次鼠标按下时触发。我drag只想在第一次鼠标按下后触发该功能一次。我应该.one()为此使用jQuery吗？

提前致谢。

Answer 1

这是即兴的，但您可以尝试：

var dragged = false;
div_paper.onmousedown = function(event) {
    var mouseCoords = getCoords(event);
    startX = mouseCoords.x - offset[0];
    startY = mouseCoords.y - offset[1];
    rect = paper.rect(startX, startY, 0, 0);
    document.onmousemove = doDraw;
    // the function below i would like to fire once
    if (!dragged)
    {
       dragged = true;
       rect.drag(drag_move, drag_start, drag_up);
    }
};