blocks|key|678488|text|var+startingNumber+=+startingNumber+%7C%7C+1;|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|678489|这就是你要找的东西，如果没有定义，它会在哪里缺省？|unstyled|678490|var+foo+=+bar+%7C%7C+1;+//+1
var+bar+=+2;
foo+=+bar+%7C%7C+1;+++++//+2|678491|顺便说一句，这适用于很多场景，包括对象：|678492|var+foo+=+bar+%7C%7C+{};+//+secure+an+object+is+assigned+when+bar+is+absent|678493|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|P|8|@]|9|@]|A|$]]|$1|G|3|H|5|6|7|Q|8|@]|9|@]|A|$B|C]]|$1|I|3|J|5|F|7|R|8|@]|9|@]|A|$]]|$1|K|3|L|5|6|7|S|8|@]|9|@]|A|$B|C]]|$1|M|3|-4|5|F|7|T|8|@]|9|@]|A|$]]]|N|$]]

<pre><code>var startingNumber = startingNumber || 1;
</code></pre>

Something like that what you're looking for, where it defaults if undefined?

<pre><code>var foo = bar || 1; // 1
var bar = 2;
foo = bar || 1; // 2
</code></pre>

By the way, this works for a lot of scenarios, including objects:

<pre><code>var foo = bar || {}; // secure an object is assigned when bar is absent
</code></pre>

blocks|key|463422|text|%7C%7C将返回它遇到的第一个真值，因此可以用作合并运算符，类似于C#的??|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|463423|startingNum+=+startingNum+%7C%7C+1;|code-block|syntax|javascript|463424|entityMap^0|0|2|X|2|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]|$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|R|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|S|8|@]|D|@]|E|$]]]|L|$]]

<code>||</code> will return the first truthy value it encounters, and can therefore be used as a coalescing operator, similar to C#'s <code>??</code>

<pre><code>startingNum = startingNum || 1;
</code></pre>

blocks|key|463681|text|在大多数现代浏览器中，您现在可以使用：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|463682|startingNum+??=+1;|code-block|syntax|javascript|463683|这只会在startingNum为null或undefined时更改它。|offset|length|style|CODE|463684|请参阅：https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Logical_nullish_assignment|463685|entityMap|0|LINK|mutability|MUTABLE|url|https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Logical_nullish_assignment^0|0|0|4|B|G|4|L|9|0|4|2U|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|X|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Y|8|@$I|Z|J|10|K|L]|$I|11|J|12|K|L]|$I|13|J|14|K|L]]|9|@]|A|$]]|$1|M|3|N|5|6|7|15|8|@]|9|@$I|16|J|17|1|18]]|A|$]]|$1|O|3|-4|5|6|7|19|8|@]|9|@]|A|$]]]|P|$Q|$5|R|S|T|A|$U|V]]]]

In most modern browsers you can now use:
<pre><code>startingNum ??= 1;
</code></pre>
This will only change <code>startingNum</code> if it is <code>null</code> or <code>undefined</code>.
See: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Logical_nullish_assignment" rel="nofollow noreferrer">https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Logical_nullish_assignment</a>

blocks|key|463465|text|var+startingNum+=+startingNum+%7C%7C+1;|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|463466|在这种情况下，可以使用OR运算符。|unstyled|463467|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|J|8|@]|9|@]|A|$]]|$1|G|3|-4|5|F|7|K|8|@]|9|@]|A|$]]]|H|$]]

<pre><code>var startingNum = startingNum || 1;
</code></pre>

In this case, you can use the OR operator.

blocks|key|463539|text|上面的答案是正确的。在JavaScript中，以下语句：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|463540|startingNum+=+startingNum+?+otherNum+:+1|code-block|syntax|javascript|463541|可以表示为|463542|startingNum+=+otherNum+%7C%7C+1|463543|这里没有介绍的另一种情况是，如果您希望值在不匹配时返回false。此操作的JavaScript简写为：|463544|startingNum+=+startingNum+?+otherNum+:+0|463545|但它可以表示为|463546|startingNum+=+startingNum+&&+otherNum|463547|只是想涵盖另一种情况，以防其他人正在寻找更通用的答案。|463548|entityMap^0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|X|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Y|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|Z|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|10|8|@]|9|@]|A|$]]|$1|M|3|N|5|D|7|11|8|@]|9|@]|A|$E|F]]|$1|O|3|P|5|6|7|12|8|@]|9|@]|A|$]]|$1|Q|3|R|5|D|7|13|8|@]|9|@]|A|$E|F]]|$1|S|3|T|5|6|7|14|8|@]|9|@]|A|$]]|$1|U|3|-4|5|6|7|15|8|@]|9|@]|A|$]]]|V|$]]

The above answers are correct. In JavaScript, the following statement:

<pre><code>startingNum = startingNum ? otherNum : 1
</code></pre>

can be expressed as 

<pre><code>startingNum = otherNum || 1
</code></pre>

Another scenario not covered here is if you want the value to return false when not matched. The JavaScript shorthand for this is:

<pre><code>startingNum = startingNum ? otherNum : 0
</code></pre>

But it can be expressed as 

<pre><code>startingNum = startingNum &amp;&amp; otherNum
</code></pre>

Just wanted to cover another scenario in case others were looking for a more generalized answer.

blocks|key|463608|text|startingNum+=+startingNum+%7C%7C+1|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|463609|如果你有一个空值的条件，比如|unstyled|463610|startingNum+=+startingNum+?+startingNum+:+null|463611|你可以使用'&&‘|463612|startingNum+=+startingNum+&&+startingNum|463613|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|P|8|@]|9|@]|A|$]]|$1|G|3|H|5|6|7|Q|8|@]|9|@]|A|$B|C]]|$1|I|3|J|5|F|7|R|8|@]|9|@]|A|$]]|$1|K|3|L|5|6|7|S|8|@]|9|@]|A|$B|C]]|$1|M|3|-4|5|F|7|T|8|@]|9|@]|A|$]]]|N|$]]

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

If you have a condition with null, like 

<pre><code>startingNum = startingNum ? startingNum : null
</code></pre>

you can use '&amp;&amp;'

<pre><code>startingNum = startingNum &amp;&amp; startingNum
</code></pre>

blocks|key|678730|text|创建一个三元组，如：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|678731|boolean_condition+?+true_result+:+false_result|code-block|syntax|javascript|678732|在javascript中，您可以执行以下操作：|678733|(boolean_condition+&&+true_result+)+%7C%7C+false_result;|678734|示例：|678735|(true+&&+'green')+%7C%7C+'red';
=>+"green"
(false+&&+'green')+%7C%7C+'red';
=>+"red"|678736|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|$]]

To make a ternary like:

<pre><code>boolean_condition ? true_result : false_result
</code></pre>

in javascript, you can do:

<pre><code>(boolean_condition &amp;&amp; true_result ) || false_result;
</code></pre>

Example:

<pre><code>(true &amp;&amp; 'green') || 'red';
=&gt; "green"
(false &amp;&amp; 'green') || 'red';
=&gt; "red"
</code></pre>

blocks|key|678828|text|您可以使用接受的答案，但它并不理想，因为它在与bools一起使用时会中断，如果您默认为true，则它将始终计算为true+->|type|unstyled|depth|inlineStyleRanges|entityRanges|data|678829|var+undefinedVal:+boolean;
var+trueVal+=+true;
var+falseVal+=+false;|code-block|syntax|javascript|678830|角度模板ex：|678831|Value+:+{{+undefinedVal+%7C%7C+true+}}+->+true
Value+:+{{+trueVal+%7C%7C+true+}}+->+true
Value+:+{{+falseVal+%7C%7C+true+}}+->+true?|678832|因此，在使用bools时，请使用较长的方法：|678833|Value+:+{{+(val+!=+null)+?+val+:+true+}}|678834|还要注意typescript和C#+(我认为)，当使用带有字符串连接的三元时，它必须放在方括号->中|678835|console.log("Value+:"+%2B+((val+!=+null)+?+val+:+true));|678836|entityMap^0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|W|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|X|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|Y|8|@]|9|@]|A|$]]|$1|M|3|N|5|D|7|Z|8|@]|9|@]|A|$E|F]]|$1|O|3|P|5|6|7|10|8|@]|9|@]|A|$]]|$1|Q|3|R|5|D|7|11|8|@]|9|@]|A|$E|F]]|$1|S|3|-4|5|6|7|12|8|@]|9|@]|A|$]]]|T|$]]

You can use the accepted answer, but it's not ideal as it breaks when used with bools, if you're defaulting to true, it will always evaluate to true -&gt;
<pre><code>var undefinedVal: boolean;
var trueVal = true;
var falseVal = false;
</code></pre>
Angular Template ex:
<pre><code>Value : {{ undefinedVal || true }} -&gt; true
Value : {{ trueVal || true }} -&gt; true
Value : {{ falseVal || true }} -&gt; true?
</code></pre>
So use the long way when using bools:
<pre><code>Value : {{ (val != null) ? val : true }}
</code></pre>
Also note for typescript and C# (I think), when using ternary with string concatenation it has to be in brackets -&gt;
<pre><code>console.log(&quot;Value :&quot; + ((val != null) ? val : true));
</code></pre>

I know that in PHP 5.3 instead of using this redundant ternary operator syntax:
<pre><code>startingNum = startingNum ? startingNum : 1
</code></pre>
...we can use a shorthand syntax for our ternary operators where applicable:
<pre><code>startingNum = startingNum ?: 1
</code></pre>
And I know about the ternary operator in JavaScript:
<pre><code>startingNum = startingNum ? startingNum : 1
</code></pre>
...but is there a shorthand?

JavaScript shorthand ternary operator

我知道在PHP5.3中没有使用这个冗余的三元运算符语法：startingNum = startingNum ? startingNum : 1在适用的情况下，...we可以为我们的三元运算符使用简写语法：startingNum = startingNum ?: 1我知道JavaScript中的三元运算符：startingNum = startingNum ? startingNum : 1...b

问JavaScript速记三元运算符
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