blocks|key|4242119|text|你应该去看看_.mergeWith。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|4242120|参考：https://github.com/lodash/lodash/issues/2499|4242121|entityMap|0|LINK|mutability|MUTABLE|url|https://lodash.com/docs/#mergeWith|1|https://github.com/lodash/lodash/issues/2499^0|6|B|0|0|3|18|1|0^^$0|@$1|2|3|4|5|6|7|P|8|@]|9|@$A|Q|B|R|1|S]]|C|$]]|$1|D|3|E|5|6|7|T|8|@]|9|@$A|U|B|V|1|W]]|C|$]]|$1|F|3|-4|5|6|7|X|8|@]|9|@]|C|$]]]|G|$H|$5|I|J|K|C|$L|M]]|N|$5|I|J|K|C|$L|O]]]]

<p>You should check out <a href="https://lodash.com/docs/#mergeWith" rel="nofollow noreferrer">_.mergeWith</a>.</p>

<p>Ref: <a href="https://github.com/lodash/lodash/issues/2499" rel="nofollow noreferrer">https://github.com/lodash/lodash/issues/2499</a></p>


blocks|key|4242213|text|可以通过使用lodash#mergeWith合并对象，并以lodash#isNil作为识别条件来确定变量是null还是undefined，从而解决此问题。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|4242214|//+Note:+if+you+change+`_.isNil`+to+`_.isUndefined`
//+then+you'd+get+the+`_.defaults()`+normal+behavior
const+nilMerge+=+(a,+b)+=>+_.isNil(a)?+b:+a;

const+nilMergeDeep+=+(a,+b)+=>+(_.isObject(a)+&&+!_.isArray(a))
++//+recursively+merge+objects+with+nilMergeDeep+customizer
++?+_.mergeWith({},+a,+b,+nilMergeDeep)+
++//+let's+use+our+default+customizer
++:+nilMerge(a,+b);

//+defaults+not+deep+with+null/undefined
const+result1+=+_.mergeWith({},+o1,+o2,+o3,+nilMerge);

//+defaults+deep+with+null/undefined
const+result2+=+_.mergeWith({},+o1,+o2,+o3,+nilMergeDeep);|code-block|syntax|javascript|4242215|​|4242216|const+o1+=+{
++a:+1,
++b:+2,
++c:+3,
++d:+null,
++x:+{
++++x1:+1,
++++x2:+2,
++++x3:+null
++},
++z:+null
};

const+o2+=+{
++a:+9999,
++d:+4,
++e:+null,
++f:+123,
++x:+{
++++x3:+3,
++++x4:+null
++},
++z:+['a',+'b']
};

const+o3+=+{
++b:+9999,
++e:+5,
++f:+2,
++g:+234,
++x:+{
++++x4:+4,
++++x5:+5,
++++x6:+['hi',+'there']
++},
++z:+['c']
};

//+Note:+if+you+change+`_.isNil`+to+`_.isUndefined`
//+then+you'd+get+the+`_.defaults()`+normal+behavior
const+nilMerge+=+(a,+b)+=>+_.isNil(a)?+b:+a;

const+nilMergeDeep+=+(a,+b)+=>+(_.isObject(a)+&&+!_.isArray(a))
++//+recursively+merge+objects+with+nilMergeDeep+customizer
++?+_.mergeWith({},+a,+b,+nilMergeDeep)+
++//+let's+use+our+default+customizer
++:+nilMerge(a,+b);

//+defaults+not+deep+with+null/undefined
const+result1+=+_.mergeWith({},+o1,+o2,+o3,+nilMerge);

//+defaults+deep+with+null/undefined
const+result2+=+_.mergeWith({},+o1,+o2,+o3,+nilMergeDeep);

console.log('defaults+not+deep+with+null/undefined');
console.log(result1);

console.log('defaults+deep+with+null/undefined');
console.log(result2);|4242217|.as-console-wrapper{min-height:100%25;top:0}|4242218|<script+src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.10/lodash.min.js"></script>|4242219|4242220|entityMap|0|LINK|mutability|MUTABLE|url|https://lodash.com/docs/4.17.10#mergeWith|1|https://lodash.com/docs/4.17.10#isNil^0|6|G|T|C|1H|4|1N|9|6|G|0|T|C|1|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|13|8|@$9|14|A|15|B|C]|$9|16|A|17|B|C]|$9|18|A|19|B|C]|$9|1A|A|1B|B|C]]|D|@$9|1C|A|1D|1|1E]|$9|1F|A|1G|1|1H]]|E|$]]|$1|F|3|G|5|H|7|1I|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|1J|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|1K|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|H|7|1L|8|@]|D|@]|E|$I|J]]|$1|Q|3|R|5|H|7|1M|8|@]|D|@]|E|$I|J]]|$1|S|3|L|5|6|7|1N|8|@]|D|@]|E|$]]|$1|T|3|-4|5|6|7|1O|8|@]|D|@]|E|$]]]|U|$V|$5|W|X|Y|E|$Z|10]]|11|$5|W|X|Y|E|$Z|12]]]]

<p>You can solve this by using <a href="https://lodash.com/docs/4.17.10#mergeWith" rel="nofollow noreferrer"><code>lodash#mergeWith</code></a> to merge objects with <a href="https://lodash.com/docs/4.17.10#isNil" rel="nofollow noreferrer"><code>lodash#isNil</code></a> as the identifying condition to determine if a variable is <code>null</code> or <code>undefined</code>.</p>

<pre><code>// Note: if you change `_.isNil` to `_.isUndefined`
// then you'd get the `_.defaults()` normal behavior
const nilMerge = (a, b) =&gt; _.isNil(a)? b: a;

const nilMergeDeep = (a, b) =&gt; (_.isObject(a) &amp;&amp; !_.isArray(a))
  // recursively merge objects with nilMergeDeep customizer
  ? _.mergeWith({}, a, b, nilMergeDeep) 
  // let's use our default customizer
  : nilMerge(a, b);

// defaults not deep with null/undefined
const result1 = _.mergeWith({}, o1, o2, o3, nilMerge);

// defaults deep with null/undefined
const result2 = _.mergeWith({}, o1, o2, o3, nilMergeDeep);
</code></pre>

<p><div class="snippet" data-lang="js" data-hide="true" data-console="true" data-babel="false">
<div class="snippet-code snippet-currently-hidden">
<pre class="snippet-code-js lang-js prettyprint-override"><code>const o1 = {
  a: 1,
  b: 2,
  c: 3,
  d: null,
  x: {
    x1: 1,
    x2: 2,
    x3: null
  },
  z: null
};

const o2 = {
  a: 9999,
  d: 4,
  e: null,
  f: 123,
  x: {
    x3: 3,
    x4: null
  },
  z: ['a', 'b']
};

const o3 = {
  b: 9999,
  e: 5,
  f: 2,
  g: 234,
  x: {
    x4: 4,
    x5: 5,
    x6: ['hi', 'there']
  },
  z: ['c']
};

// Note: if you change `_.isNil` to `_.isUndefined`
// then you'd get the `_.defaults()` normal behavior
const nilMerge = (a, b) =&gt; _.isNil(a)? b: a;

const nilMergeDeep = (a, b) =&gt; (_.isObject(a) &amp;&amp; !_.isArray(a))
  // recursively merge objects with nilMergeDeep customizer
  ? _.mergeWith({}, a, b, nilMergeDeep) 
  // let's use our default customizer
  : nilMerge(a, b);

// defaults not deep with null/undefined
const result1 = _.mergeWith({}, o1, o2, o3, nilMerge);

// defaults deep with null/undefined
const result2 = _.mergeWith({}, o1, o2, o3, nilMergeDeep);

console.log('defaults not deep with null/undefined');
console.log(result1);

console.log('defaults deep with null/undefined');
console.log(result2);</code></pre>
<pre class="snippet-code-css lang-css prettyprint-override"><code>.as-console-wrapper{min-height:100%;top:0}</code></pre>
<pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.10/lodash.min.js"&gt;&lt;/script&gt;</code></pre>
</div>
</div>
</p>


<p>I'm looking for versions of Lodash's <a href="https://lodash.com/docs/4.17.10#defaults" rel="nofollow noreferrer"><code>defaults</code></a> and <a href="https://lodash.com/docs/4.17.10#defaultsDeep" rel="nofollow noreferrer"><code>defaultsDeep</code></a> that override <code>null</code> values in addition to <code>undefined</code>. I've looked at the source for <code>defaultsDeep</code> but couldn't figure out a simple way to get it working. I'd rather use a simple solution, possibly based on Lodash, than roll my own.</p>


Versions of defaultDeep and defaults that override undefined and null values

我正在寻找除了null之外还能覆盖undefined值的Lodash的和版本。我看过defaultsDeep的源代码，但找不到一种简单的方法来让它工作。我宁愿使用一个简单的解决方案，可能基于Lodash，而不是使用我自己的解决方案。

问覆盖未定义和空值的defaultDeep和默认值的版本
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