javascript - 在其他函数中仅执行一次函数

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，每次鼠标按下时都会触发。我只想在第一次鼠标按下后触发一次 drag 函数。我应该使用 jQuery .one() 吗？

提前致谢。

Answer 1

这是即兴的，但你可以尝试:

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);
    }
};