其它函數中執行功能只有一次

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); 
}; 

其火，你可以看到，在每個鼠標按下。我想在第一個mousedown之後只能觸發drag函數一次。我應該使用jQuery .one()嗎？

在此先感謝。

Answer 1

這是即興的，但你可以嘗試：

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); 
    } 
};