jQuery在元素内检测mousedown，然后在元素外检测mouseup

问题描述

我有一些类似于绘图画布的东西，我在 mouseup 上捕获它的状态以用于撤消目的.画布不是全屏的，因此您可以使用画笔绘制并在画布外释放.像这样的:

I have something similar to a drawing canvas, and I capture it's state on mouseup for undo purposes. The canvas isn't full screen, so you can draw with a brush and release outside the canvas. Something like this:

$("#element").mousedown(function(){
  $(document).mouseup(function(){
    //do something
  }); 
});

但这当然行不通.普通的 $(document).mouseup 也不起作用，因为我还有许多其他 UI 元素，并且每次单击 UI 元素时它都会保存状态.

But this doesn't work of course. A plain $(document).mouseup doesn't work either, because I have many other UI elements and it saves the state each time you click on a UI element.

有什么想法吗?

推荐答案

var isDown = false;

$("#element").mousedown(function(){
    isDown = true;
});

$(document).mouseup(function(){
    if(isDown){
        //do something
        isDown = false;
    }
}); 

为了简单起见，我将 isDown 放在全局命名空间中.在生产中，您可能希望隔离该变量的范围.

For the sake of simplicity I put isDown in the global namespace. In production you would probably want to isolate the scope of that variable.

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