更改子局部函数中全局变量的值 javascript

Question

此代码的大部分内容无需解释。如您所见，全局变量 cancel 设置为 true。然后调用一个函数，其中变量 cancel 被更改。 好像我可以在第 15、27 或 32 行访问 cancel 变量。 你能解释一下为什么它不起作用以及我该如何解决它吗？谢谢！请提出任何其他问题。我没有在这里解释其他代码，因为我认为它不直接与问题相关，如果我是，它会使这个问题太长而无法阅读。

1. var cancel = 'true';
2. function setSliders()
3. {
4.  var sliders = document.getElementsByClassName('slider');
5.  var sliderButtons = document.getElementsByClassName('sliderButton');
6.  for(var i = 0; i != sliderButtons.length; i++)
7.  {
8.      var slider = document.getElementsByClassName('sliderButton')[i];
9.      slider.onmousedown = function()
10.     {
11.         cancel = 'false';
12.         this.onmouseup = function(cancel)
13.         {
14.             cancel = 'true';
15.             alert(cancel +' within semi function cancel does not seem to be accessible here');
16.             //alert('test');
17.         };
18.         
19.         alert(cancel+' within function');
20.         
21.         this.onmousemove = function(event, cancel)
22.         {
23.             if(cancel == 'false')
24.             {
25.                 console.log('cancel is false'); //cancel doesn't seem to be accessible here either.
26.                 this.style.left = event.clientX+'px';
27.                 cancel = 'true';
28.             }
29.             else
30.             {
31.                 console.log('cancel is true'); //cancel isn't accessible here either.
32.                 cancel = 'false';
33.             }
34.         };
35.     };

Answer 1

您将 cancel 作为函数的参数名称，使这些函数中的 cancel 成为该函数的局部变量。

如果您从参数中删除 cancel，它将引用全局 cancel 变量并且应该可以工作。

1. var cancel = 'true';
2. function setSliders()
3. {
4.  var sliders = document.getElementsByClassName('slider');
5.  var sliderButtons = document.getElementsByClassName('sliderButton');
6.  for(var i = 0; i != sliderButtons.length; i++)
7.  {
8.      var slider = document.getElementsByClassName('sliderButton')[i];
9.      slider.onmousedown = function()
10.     {
11.         cancel = 'false';
12.         this.onmouseup = function()
13.         {
14.             cancel = 'true';
15.             alert(cancel +' within semi function cancel does not seem to be accessible here');
16.             //alert('test');
17.         };
18.         
19.         alert(cancel+' within function');
20.         
21.         this.onmousemove = function(event)
22.         {
23.             if(cancel == 'false')
24.             {
25.                 console.log('cancel is false'); //cancel doesn't seem to be accessible here either.
26.                 this.style.left = event.clientX+'px';
27.                 cancel = 'true';
28.             }
29.             else
30.             {
31.                 console.log('cancel is true'); //cancel isn't accessible here either.
32.                 cancel = 'false';
33.             }
34.         };
35.     };

更改子局部函数中全局变量的值 javascript

Changing value of global variable in sub local function javascript

javascript

variables

global-variables