从JavaScript对象中递归删除空值 [英] Recursively remove null values from JavaScript object

问题描述

我有一个JSON obj，经过一些操作（比如删除一些部分），我打印它，一切看起来不错，除了我有一些 null 值。如何删除这些？

I have a JSON obj, after some operations (like delete some pieces), I print it and everything looks good except that I have some null values. How do I remove these?

我使用 JSON.stringify（obj，null，2）方法进行打印，以下是它的样子：

I use JSON.stringify(obj, null, 2) method to print, and here is what it looks like:

{
    "store": {
        "book": [
             null,
             {
                 "category": "fiction",
                 "author": "Evelyn Waugh",
                 "title": "Sword of Honour",
                 "price": 12.99
             },
             null,
             {
                  "category": "fiction",
                  "author": "J. R. R. Tolkien",
                  "title": "The Lord of the Rings",
                  "isbn": "0-395-19395-8",
                  "price": 22.99
             }
        ],
        "bicycle": {
             "color": "red",
             null,
             "price": 19.95
        }
    }
}

我希望它紧凑而漂亮clean（删除额外的3 null 值）：

I want it to be much compact and pretty clean(remove the extra 3 null values):

{
    "store": {
        "book": [
             {
                 "category": "fiction",
                 "author": "Evelyn Waugh",
                 "title": "Sword of Honour",
                 "price": 12.99
             },
             {
                  "category": "fiction",
                  "author": "J. R. R. Tolkien",
                  "title": "The Lord of the Rings",
                  "isbn": "0-395-19395-8",
                  "price": 22.99
             }
        ],
        "bicycle": {
             "color": "red",
             "price": 19.95
        }
    }
}

推荐答案

我必须解决类似的问题，但是我不仅要删除 null 值，还要删除未定义， NaN ，空字符串，为空通过检查嵌套对象和嵌套数组，递归地返回数组和空对象值。

I had to solve a similar problem, however I wanted to remove not only null values but also undefined, NaN, empty String, empty array and empty object values, recursively, by inspecting nested objects and also nested arrays.

以下函数正在使用Lo-短划线：

The following function is using Lo-Dash:

function pruneEmpty(obj) {
  return function prune(current) {
    _.forOwn(current, function (value, key) {
      if (_.isUndefined(value) || _.isNull(value) || _.isNaN(value) ||
        (_.isString(value) && _.isEmpty(value)) ||
        (_.isObject(value) && _.isEmpty(prune(value)))) {

        delete current[key];
      }
    });
    // remove any leftover undefined values from the delete 
    // operation on an array
    if (_.isArray(current)) _.pull(current, undefined);

    return current;

  }(_.cloneDeep(obj));  // Do not modify the original object, create a clone instead
}

例如，如果使用以下输入对象调用该方法：

For example, if you invoke the method with the following input object:

var dirty = {
  key1: 'AAA',
  key2: {
    key21: 'BBB'
  },
  key3: {
    key31: true,
    key32: false
  },
  key4: {
    key41: undefined,
    key42: null,
    key43: [],
    key44: {},
    key45: {
      key451: NaN,
      key452: {
        key4521: {}
      },
      key453: [ {foo: {}, bar:''}, NaN, null, undefined ]
    },
    key46: ''
  },
  key5: {
    key51: 1,
    key52: '  ',
    key53: [1, '2', {}, []],
    key54: [{ foo: { bar: true, baz: null }}, { foo: { bar: '', baz: 0 }}]
  },
  key6: function () {}
};

它会以递归方式丢弃所有坏值，最后只保留那些值一些信息。

It'll recursively discard all the "bad" values, keeping in the end only the ones that carry some information.

var clean = pruneEmpty(dirty);
console.log(JSON.stringify(clean, null, 2));

{
  key1: 'AAA',
  key2: {
    key21: 'BBB'
  },
  key3: {
    key31: true,
    key32: false
  },
  key5: {
    key51: 1,
    key52: '  ',
    key53: [1, '2'],
    key54: [{ foo: { bar: true }}, { foo: { baz: 0 }}]
  }
};

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