Javascript:字典 'key' 值在 for 循环之外变为 null

Question

我有一个函数，它接受字典列表[{}]作为参数。它通过添加一个新的 key: value 对来操作这个字典列表，其中 value 也是一个字典列表。这就是该函数的样子，我添加了注释来解释它。

function addFilesToProjects(nonUniqueArray, lists) {
    var fileList = [{}]; //this will contain the list of dictionaries that I want to add as a key to the array 'nonUniqueArray'
    var filesArray = []; //this was just for testing purposes because I want to access the modified version of nonUniqueArray outside the function, which I'm not able to (it shows undefined for the new key:value pair)
    for (var i = 0; i < nonUniqueArray.length; i++) {
        lists.forEach(function (list) {
            fileNameString = JSON.stringify(list['name']).slice(2, -2);
            if (fileNameString.indexOf(nonUniqueArray[i]['title']) !== -1 && fileNameString !== nonUniqueArray[i]['title']) {
                fileList.push({
                    'name': fileNameString
                });
            }
        });
        nonUniqueArray[i]['files'] = fileList;

        //this logs out the right key:value pair to the console
        console.log(nonUniqueArray[i]);

        filesArray.push(nonUniqueArray[i]);
        while (fileList.length > 0) {
            fileList.pop();
        }
    }

    //however, now I get everything as before except the new 'files' key has empty list [] as its value :( 
    console.log(nonUniqueArray);

    return filesArray;
}

我不知道为什么会发生这种情况，有人可以帮忙吗？

Answer 1

您似乎认为您正在将 fileList 的副本添加到每个字典中，但实际上正在添加相同 fileList 到每个(即，每个都是对同一对象的引用)中，这样，正如 @vlaz 指出的那样，当您清空原始文件时，您实际上清空了每个字典中出现的内容。