Question

我在javascript有点新，所以我有一个给定数组的函数，它从传递的参数中过滤其元素。我需要的是制作这个＆＃39;在回调函数内部，在我的originalArray上进行引用，以便console.log(this);实际打印[1,2,3]。请记住，我在这些行中实际需要这个，因为我只能编辑所有这些行而不再添加更多行。

这是我的代码：

function makeMultiFilter(array) {
    // What we track
    // TO BE COMPLETED
   // TO BE COMPLETED
    return (function arrayFilterer(pred, callback) {


        // If filter not a function return current Array
        // TO BE COMPLETED
            // TO BE COMPLETED
        // Filter out things
        // TO BE COMPLETED

        // If callback is a function, execute callback
        // TO BE COMPLETED
        // TO BE COMPLETED
            return arrayFilterer;
    });
}

测试代码：

var arrayFilterer = makeMultiFilter([1, 2, 3]);
// call arrayFilterer to filter out all the numbers not equal to 2
arrayFilterer(function(elem) {

    return elem != 2; // check if element is not equal to 2
}, function(currentArray) {
    console.log(this); // prints [1,2 3]
    console.log(currentArray);
}); // prints [1, 3]`

Answer 1

您可以使用call执行给定this上下文中的函数：

＆＃13;

var callback = function() {
  console.log(this);
  console.log(arguments);
};

// Using call
callback.call([1,2,3], "A", "B", "C");

// Using apply
callback.apply([1,2,3], ["A", "B", "C"]);

// Using bind:
//  creates a new function bound to [1,2,3]
callback.bind([1,2,3])("A", "B", "C");
callback.bind([1,2,3], "A")("B", "C"); // etc.

＆＃13;

我想在您的示例代码中，这意味着您不会使用callback()，而是使用callback.call(originalArray)：

＆＃13;

function makeMultiFilter(array) {
    // What we track
    var originalArray = array;
    var currentArray = originalArray;
    return (function arrayFilterer(pred, callback) {
        // If filter not a function return current Array
        if (typeof pred !== "function")
            return currentArray;
        // Filter out things
        currentArray = currentArray.filter(pred);

        // If callback is a function, execute callback
        if (typeof callback === "function")
            callback.call(originalArray, currentArray);
            return arrayFilterer;
    });
}

var arrayFilterer = makeMultiFilter([1, 2, 3]);

// call arrayFilterer to filter out all the numbers not equal to 2
arrayFilterer(function(elem) {
    return elem != 2; // check if element is not equal to 2
}, function(currentArray) {
    console.log(this); // prints [1,2 3]
    console.log(currentArray); // prints [1,3]
}); // prints [1, 3]`

＆＃13;

访问＆＃39;这个＆＃39;回调内部应该引用我的数组

1 个答案: