Question

（我找不到open Lodash Slack频道，这就是我在这里发帖的原因。）

你能否告诉我为什么fiddle中的partialRight似乎无能为力？ correctRenameKeys函数正确地重命名了提供的object中的键，但wrongRenameKeys函数 - 应该完全相同 - 不会。

请在浏览器中打开JavaScript控制台，以便在运行小提琴时查看日志。我在Chrome中测试了它。

    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

lodash文档中有两个支持声明可以回答您的问题：

lodash#partialRight

除了部分应用的参数外，此方法与_.partial类似被附加到它收到的参数。

lodash#map

通过运行集合中的每个元素来创建值数组 iteratee。使用三个参数调用iteratee :( value， index | key，collection）。

请注意，在lodash#map iteratee中传递了三个参数，并且因为keyRenamer作为iteratee传递，所以我们可以得出结论：调用签名看起来像这样：

keyRenamer(value, index, collection, keyMappings);

如果你真的希望实现部分应用函数renameKeysOfOneObject的第二个参数的效果，那么使用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>

Lodash的partialRight似乎什么都不做

1 个答案: