将参数传递给KeyDown [英] Passing Parameters to KeyDown

问题描述

如何从jquery将参数传递到keydown方法中，因为每当我使用在其他地方定义的变量时，它都会返回未定义的值.我以为它是因为#target是窗口，因此它不在范围内，但是即使那样，我仍然很难使它将key.which()与外部参数进行比较，然后将其分配给另一个属性.

How can you pass parameters into the keydown method from jquery because whenever I use a variable defined elsewhere it returns undefined. I assume its because the #target is window and therefore its not in the scope but even then I have trouble getting it to compare the key.which() with an outside parameter and then assigning it to another property.

示例:

var a = 38;
var b = 0;
$(document).keydown(function(e){
  var key = e.which;
  if (a==key)
    b=key;
});
console.log(a+""+b);

每当我尝试执行相同操作时，它会返回38 0，我将其解释为不在范围内且未定义(这也是因为如果我登录b，它将在keydown函数中打印未定义)?我怎样才能通过?

Whenever I try to do something along the same lines it returns 38 0 which I interpreted as it not being in the scope and being undefined (also because if I log b it prints undefined in the keydown func)? How could I pass in a?

推荐答案

您console.log无法正常工作，因为它在脚本加载时已初始化.您需要做的就是在按下该键时触发功能.

You console.log is not working because it is initialized when the script load. What you need to do is to trigger your functions when the key is pressed.

// When the document is ready
$(function() {
   $(document).keydown(function(e){
      var key = e.which;
      var a = 'a scoped variable';
      switch (key) {
          // Up arrow
          case 38: 
             a = upArrowFunction(a); // Assign a to the returned value.
             break;
          // Down arrow
          case 40:
             downArrowFunction();
             break;
      }

   });

   function upArraowFunction(a) {
       a = 'I change a, but a is not changed in keydown event';
       return a; // But now I return the changed variable so it will change if a variable is assigned where the function is called.
   }

   function downArrowFunction() {
       // Do something else
   }
});

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