javascript - 如何在闭包中使用 'uncapture' 变量？

Question

我正在尝试使用规则对象添加事件监听器，如下所示

keyMap = [
    {name: "Up", type: "keydown", code: 87, action: function(){alert("up")}},
    {name: "Down", type: "keydown", code: 83, action: function(){alert("down")}},
    {name: "Left", type: "keydown", code: 65, action: function(){alert("left")}},
    {name: "Right", type: "keydown", code: 68, action: function(){alert("right")}}
]

for(var keyAct of keyMap){
    if( typeof keyAct.action === "function" ){
         document.addEventListener(keyAct.type, function(e){
            if(e.keyCode === keyAct.code){
                keyAct.action(e);
            }
         });
    }
}

然后w/a/s/d按所有警报“右”。我重写了 for 部分，如下所示:

for(var keyAct of keyMap){
    (function(keyAct){
        if( typeof keyAct.action === "function" ){
             document.addEventListener(keyAct.type, function(e){
                if(e.keyCode === keyAct.code){
                    keyAct.action(e);
                }
             });
        }
    })(keyAct);
}

它确实有效，但这是唯一的方法吗？我可以做得更优雅吗？我的意思是，这看起来很奇怪。

Answer 1

创建另一个函数来绑定(bind)事件，试试这个:

for(var i = 0, len = keyMap.length; i < len; ++i) {
    if( typeof keyMap[i].action === "function" ) {
        binder(keyMap[i]);
    }
}

function binder(keyAct) {
    document.addEventListener(keyAct.type, function(e) {
        if(e.keyCode === keyAct.code) {
            keyAct.action(e);
        }
    });
}