為什么我必須在閉包中聲明一個函數，訪問閉包中定義的變量？

Question

為什么我必須在閉包中聲明一個函數才能訪問閉包中的變量？ 我希望我能夠在閉包之外定義函數，但可以在閉包周圍進行定義，並提供所需的變量，但是除非函數實際上是在閉包內定義的，否則變量不可用。

http://jsfiddle.net/c5oba93a/1/

//reusable function defined outside of closure, I want to swap out myMethod within this function.
var reusableFunction = function () {
    //common code
    try {
        console.log(myVar);
        myMethod.call(this);
    } catch (e) {
        console.log(e);
    }
    //common code
};


var functOneForClosure = function () {
    console.log('functOne');
};
var functTwoForClosure = function () {
    console.log('functTwo');
};

//myMethod and myVar are undefined in reusableFunction
(function () {
    var myMethod = functOneForClosure;
    var myVar = 'variable in closure with functOne';
    return reusableFunction;
})()();
(function (myMethodIn) {
    var myMethod = myMethodIn;
    var myVar = 'variable in closure with functTwo';
    return reusableFunction;
})(functOneForClosure)();

//if the function is defined within the closure it behaves as expected.
var getReusableVersion =(function (myMethod) {
    var myVar = 'defining function within closure makes the difference';
    return function () {
        //common code
        try {
            console.log(myVar);
            myMethod.call(this);
        } catch (e) {
            console.log(e);
        }
        //common code
    };
});

getReusableVersion(functOneForClosure)();

Answer 1

@pherris根據您之前的評論：這無濟於事。 在this的IIFEs內指的是window對象，現在你有附加屬性的垃圾郵件了。 但是reusableFunction myVar and myMethod仍未定義，您必須改用this.myVar和this.myMethod 。 比向窗口發送垃圾更好的是將vars作為參數傳遞：

var reusableFunction = function (myVar, myMethod) {
    // no try/catch needed anymore
    console.log(myVar);
    if (typeof myMethod == 'function') myMethod.call(this);
    else console.log(myMethod);
};

現在，有兩種方法可以用IIFE調用它。

第一個從IIFE返回帶有綁定參數的函數，然后執行該函數：

(function () {
    var myMethod = functOneForClosure;
    var myVar = 'variable in closure with functOne';

    // first argument of .bind() appears in the function as 'this',
    // the others appear as fixed arguments of the function
    return reusableFunction.bind(window, myVar, myMethod);
})()();

第二種方法在IIFE中調用它，因此之后的調用被刪除：

(function () {
    var myMethod = functOneForClosure;
    var myVar = 'variable in closure with functOne';

    return reusableFunction(myVar, myMethod);

    // of course its possible to call on 'this', but that doesn't change anything:
    /* return reusableFunction.call(this, myVar, myMethod); */

})();