洛达什的partialRight似乎什么都没做

Question

(我找不到打开 Lodash Slack频道，这就是我在这里发帖的原因。)

你能告诉我为什么这个小提琴中的小提琴似乎什么都不做吗？correctRenameKeys函数正确地重命名了提供的object中的键，但是wrongRenameKeys函数--应该完全相同--却没有。

在运行小提琴时，请打开浏览器中的JavaScript控制台以查看日志。我在Chrome里测试过。

​

    const renameKeysOfOneObject = (object, keyMappings) => {
      return _.reduce(object, function(result, value, key) {
        key = keyMappings[key] || key;
        result[key] = value;
        return result;
      }, {});
    };

    const correctRenameKeys = (objects, keyMappings) => {
        const keysRenamer = object => renameKeysOfOneObject(object, keyMappings);
        return _.map(objects, keysRenamer);
    };

    const wrongRenameKeys = (objects, keyMappings) => {
        const keysRenamer = _.partialRight(renameKeysOfOneObject, keyMappings);
        return _.map(objects, keysRenamer);
    };

    const object = {keyToBeRenamed: 'someValue'};
    const objects = [object];
    const keyMapping = {keyToBeRenamed: 'newKeyName'};

    const correctlyRenamed = correctRenameKeys(objects, keyMapping);
    const wronglyRenamed = wrongRenameKeys(objects, keyMapping);

    console.assert(_.isEqual(correctlyRenamed, wronglyRenamed), 
                   "The two objects should be equal. " + 
                   "The 'keyToBeRenamed' key should have been renamed to 'newKeyName'.");
    console.log(correctlyRenamed);
    console.log(wronglyRenamed);

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.min.js"></script>

​

Answer 1

提交文件中有两种支持声明可以回答您的问题：

lodash#partialRight

此方法与_.partial类似，只是部分应用的参数被附加到它接收的参数中。

lodash#map

通过通过iteratee集合中的每个元素来创建一个值数组。迭代器是使用三个参数调用的：(value、Index而行键、集合)。

请注意，在lodash#map迭代器中传递了三个参数，而且由于keyRenamer是作为迭代传递的，所以我们可以得出结论，调用签名如下所示：

keyRenamer(value, index, collection, keyMappings);

如果您真的想实现部分应用函数renameKeysOfOneObject的第二个参数的效果，那么请使用lodash#partial。

const wrongRenameKeys = (objects, keyMappings) => {
    const keysRenamer = _.partial(renameKeysOfOneObject, _, keyMappings);
    return _.map(objects, keysRenamer);
};

​

const renameKeysOfOneObject = (object, keyMappings) => {
      return _.reduce(object, function(result, value, key) {
        key = keyMappings[key] || key;
        result[key] = value;
        return result;
      }, {});
    };

    const correctRenameKeys = (objects, keyMappings) => {
        const keysRenamer = object => renameKeysOfOneObject(object, keyMappings);
        return _.map(objects, keysRenamer);
    };

    const wrongRenameKeys = (objects, keyMappings) => {
        const keysRenamer = _.partial(renameKeysOfOneObject, _, keyMappings);
        return _.map(objects, keysRenamer);
    };

    const object = {keyToBeRenamed: 'someValue'};
    const objects = [object];
    const keyMapping = {keyToBeRenamed: 'newKeyName'};

    const correctlyRenamed = correctRenameKeys(objects, keyMapping);
    const wronglyRenamed = wrongRenameKeys(objects, keyMapping);

    console.assert(_.isEqual(correctlyRenamed, wronglyRenamed), 
                   "The two objects should be equal. " + 
                   "The 'keyToBeRenamed' key should have been renamed to 'newKeyName'.");
    console.log(correctlyRenamed);
    console.log(wronglyRenamed);

.as-console-wrapper{min-height:100%;top:0}

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.min.js"></script>

​