blocks|key|182511|text|两者都是绝对正确的，但如果你在寻找像红宝石中的%7C%7C=那样的东西。第一个方法是variable+=+variable+%7C%7C+{}，您要寻找的方法是:)|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|182512|entityMap^0|N|3|12|P|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|M|8|@]|D|@]|E|$]]]|G|$]]

Both are absolutely correct, but if you are looking for something that works like <code>||=</code> in ruby. The first method which is <code>variable = variable || {}</code> is the one you are looking for :)

blocks|key|182522|text|您可以使用逻辑OR运算符%7C%7C，如果lVal是falsy值，则计算其右操作数。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|182523|Falsy值包括例如null,+false,+0,+"",+undefined,+NaN|182524|x+=+x+%7C%7C+1|code-block|syntax|javascript|182525|entityMap^0|C|2|H|4|0|A|Y|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]|$9|R|A|S|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|T|8|@$9|U|A|V|B|C]]|D|@]|E|$]]|$1|H|3|I|5|J|7|W|8|@]|D|@]|E|$K|L]]|$1|M|3|-4|5|6|7|X|8|@]|D|@]|E|$]]]|N|$]]

You can use the logical OR operator <code>||</code> which evaluates its right operand if <code>lVal</code> is a falsy value.

Falsy values include e.g <code>null, false, 0, "", undefined, NaN</code>

<pre><code>x = x || 1
</code></pre>

blocks|key|182578|text|你问的关于已被认为是JavaScript中的一项功能。的接线员。它目前在第4阶段，它将是在下一个ECMAScript标准中引入，预计将于2021年出版。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|182579|您现在可以使用插件-建议-逻辑分配-运算符Babel插件使用它。我从来没有使用过那个插件，所以我不知道它有多好。|182580|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/tc39/proposal-logical-assignment|1|https://tc39.es/process-document/|2|https://github.com/tc39/proposals/blob/master/finished-proposals.md|3|https://babeljs.io/docs/en/babel-plugin-proposal-logical-assignment-operators^0|5|M|0|10|4|1|18|J|2|0|7|L|3|0^^$0|@$1|2|3|4|5|6|7|T|8|@]|9|@$A|U|B|V|1|W]|$A|X|B|Y|1|Z]|$A|10|B|11|1|12]]|C|$]]|$1|D|3|E|5|6|7|13|8|@]|9|@$A|14|B|15|1|16]]|C|$]]|$1|F|3|-4|5|6|7|17|8|@]|9|@]|C|$]]]|G|$H|$5|I|J|K|C|$L|M]]|N|$5|I|J|K|C|$L|O]]|P|$5|I|J|K|C|$L|Q]]|R|$5|I|J|K|C|$L|S]]]]

The operator you asked about <a href="https://github.com/tc39/proposal-logical-assignment" rel="nofollow noreferrer">has been proposed as a feature in JavaScript</a>. It is currently at <a href="https://tc39.es/process-document/" rel="nofollow noreferrer">Stage 4</a>, and it will be <a href="https://github.com/tc39/proposals/blob/master/finished-proposals.md" rel="nofollow noreferrer">introduced in the next ECMAScript standard</a>, which is expected to be published in 2021.
You can use it now using <a href="https://babeljs.io/docs/en/babel-plugin-proposal-logical-assignment-operators" rel="nofollow noreferrer">the plugin-proposal-logical-assignment-operators Babel plugin</a>. I have never used that plugin, so I have no idea how well it works.

blocks|key|1210493|text|如果您正在处理对象，可以使用析构(因为ES6)，如下所示：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1210494|({+myLib:+window.myLib+=+{}+}+=+window);|code-block|syntax|javascript|1210495|...but，除了困惑之外，你不会从被接受的答案中得到任何东西。|1210496|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

If you're working with objects, you can use destructuring (since ES6) like so:

<pre><code>({ myLib: window.myLib = {} } = window);
</code></pre>

...but you don't gain anything over the accepted answer except confusion.

blocks|key|182597|text|逻辑无效赋值(??=)|type|unstyled|depth|inlineStyleRanges|entityRanges|data|182598|x+??=+23|code-block|syntax|javascript|182599|文档和浏览器兼容性|offset|length|182600|entityMap|0|LINK|mutability|MUTABLE|url|https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Logical_nullish_assignment^0|0|0|0|9|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|U|8|@]|9|@$I|V|J|W|1|X]]|A|$]]|$1|K|3|-4|5|6|7|Y|8|@]|9|@]|A|$]]]|L|$M|$5|N|O|P|A|$Q|R]]]]

<h2>Logical nullish assignment (??=)</h2>
<pre class="lang-js prettyprint-override"><code>x ??= 23
</code></pre>
<a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Logical_nullish_assignment" rel="nofollow noreferrer">Documentation &amp; Browser compatibility</a>

blocks|key|182602|text|从2021年起，只要您正在转换或者不关心Opera/IE，就可以使用与Ruby行为相同的%7C%7C=。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|182603|逻辑或分配，%7C%7C=现在被支持在javascript的所有主要浏览器上，除了Opera和IE。电流曲线矩阵。MDN参考。|182604|类型记录在第4版中增加了对运算符的支持。如果您需要支持IE/Opera，可以使用babel插件来实现广泛的兼容性。|182605|entityMap|0|LINK|mutability|MUTABLE|url|https://caniuse.com/?search=logical%2520assignment|1|https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Logical_OR_assignment|2|https://devblogs.microsoft.com/typescript/announcing-typescript-4-0/#short-circuiting-assignment-operators|3^0|18|3|0|6|3|1A|6|0|1H|5|1|0|5|3|2|14|7|3|0^^$0|@$1|2|3|4|5|6|7|W|8|@$9|X|A|Y|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|Z|8|@$9|10|A|11|B|C]]|D|@$9|12|A|13|1|14]|$9|15|A|16|1|17]]|E|$]]|$1|H|3|I|5|6|7|18|8|@]|D|@$9|19|A|1A|1|1B]|$9|1C|A|1D|1|1E]]|E|$]]|$1|J|3|-4|5|6|7|1F|8|@]|D|@]|E|$]]]|K|$L|$5|M|N|O|E|$P|Q]]|R|$5|M|N|O|E|$P|S]]|T|$5|M|N|O|E|$P|U]]|V|$5|M|N|O|E|$P|U]]]]

As of 2021, you can use <code>||=</code> with identical behavior to Ruby as long as you are transpiling or don't care about Opera/IE.
Logical OR assignement, <code>||=</code> is now supported natively in javascript on all major browsers except Opera and IE. <a href="https://caniuse.com/?search=logical%20assignment" rel="nofollow noreferrer">Current caniuse matrix</a>. <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Logical_OR_assignment" rel="nofollow noreferrer">MDN reference</a>.
Typescript added support for the operator in <a href="https://devblogs.microsoft.com/typescript/announcing-typescript-4-0/#short-circuiting-assignment-operators" rel="nofollow noreferrer">version 4</a>. If you need to support IE/Opera you can use the <a href="https://devblogs.microsoft.com/typescript/announcing-typescript-4-0/#short-circuiting-assignment-operators" rel="nofollow noreferrer">babel plugin</a> to transpile for broad compatibility.

blocks|key|2287346|text|鲁比的%7C%7C=算子短路分配。可以这样想：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2287347|return+a+%7C%7C+a+=+b|code-block|syntax|javascript|2287348|因此，在javascript中，这看起来非常相似：|2287349|return+a+%7C%7C+(a+=+b);|2287350|然而，正如在下面的注释中所指出的，这个文字的ruby形式比标准的javascript成语a=a\x\+b效率低。|2287351|参考：http://www.rubyinside.com/what-rubys-double-pipe-or-equals-really-does-5488.html|offset|length|2287352|entityMap|0|LINK|mutability|MUTABLE|url|http://www.rubyinside.com/what-rubys-double-pipe-or-equals-really-does-5488.html^0|0|0|0|0|0|3|28|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|Z|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|10|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|11|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|12|8|@]|9|@]|A|$]]|$1|M|3|N|5|6|7|13|8|@]|9|@$O|14|P|15|1|16]]|A|$]]|$1|Q|3|-4|5|6|7|17|8|@]|9|@]|A|$]]]|R|$S|$5|T|U|V|A|$W|X]]]]

Ruby's ||= operator short circuits assignment. It can be thought of like this:

<pre><code>return a || a = b
</code></pre>

So in javascript, this looks very similar:

<pre><code>return a || (a = b);
</code></pre>

It seems as pointed out in the comments below however, that this literal ruby form is less efficient than the standard javascript idiom a = a || b.

For reference:
<a href="http://www.rubyinside.com/what-rubys-double-pipe-or-equals-really-does-5488.html" rel="nofollow">http://www.rubyinside.com/what-rubys-double-pipe-or-equals-really-does-5488.html</a>

blocks|key|182589|text|您可以使用javascript中仅针对整数的%7C=操作符实现所需的行为。但是你必须先定义变量。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|182590|let+a+=+0
a+%7C=+100
console.log(a)+//+100|code-block|syntax|javascript|182591|用于对象|182592|let+o+=+{}
o.a+%7C=+100
console.log(o)+//+{a:+100}|182593|用于数组|182594|let+arr+=+[]
arr[0]+%7C=+100
console.log(arr)+//+[100]|182595|entityMap^0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|S|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|U|8|@]|9|@]|A|$]]|$1|M|3|N|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|O|3|-4|5|6|7|W|8|@]|9|@]|A|$]]]|P|$]]

You can achieve the desired behaviour using |= operator in javascript for integers only. But you have to define the variable first.
<pre><code>let a = 0
a |= 100
console.log(a) // 100
</code></pre>
For objects
<pre><code>let o = {}
o.a |= 100
console.log(o) // {a: 100}
</code></pre>
For Arrays
<pre><code>let arr = []
arr[0] |= 100
console.log(arr) // [100]
</code></pre>

I love Ruby's <code>||=</code> mechanism. If a variable doesn't exist or is <code>nil</code>, then create it and set it equal to something:

<pre><code>amount # is nil
amount ||= 0 # is 0
amount ||= 5 # is 0
</code></pre>

I need to do something similar in JavaScript now. What's the convention or proper way to do this? I know <code>||=</code> is not valid syntax. 2 obvious ways to handle it are:

<pre><code>window.myLib = window.myLib || {};

// or

if (!window.myLib)
 window.myLib = {};
</code></pre>

Ruby's ||= (or equals) in JavaScript?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我喜欢Ruby的||=机制。如果一个变量不存在或是nil，那么创建它并将其设置为等于：amount # is nilamount ||= 0 # is 0amount ||= 5 # is 0我现在需要在JavaScript中做一些类似的事情。有什么惯例或适当的方法来做这件事？我知道||=不是有效的语法。处理这一问题的两个明显方法是：window.myLib = window.myLib || {

问Ruby的||= (或等于)在JavaScript中？
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