blocks|key|355016|text|最好始终保持与约定一致。要么全是分号，要么全是逗号，我肯定你更喜欢使用分号，而不是到处都是逗号。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|355017|也没有速度增益，所以没什么好担心的。|355018|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

It's best to always remain consistent with convention. It's either all semi-colons or all commas, and I'm sure you'd prefer to use semi-colons rather than commas everywhere.

There is no speed gain as well, so there's nothing to worry about.

blocks|key|137223|text|逗号运算符是可以在表达式中使用的运算符。它用于分离出多个不同的表达式，其含义是“计算以下所有表达式，然后生成最终表达式的值”。例如：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|137224|a+=+1,+b+=+2,+c+=+3|code-block|syntax|javascript|137225|表示“计算a+=+1，然后是b+=+2，然后是c+=+3，然后计算为表达式c+=+3的值。|offset|length|style|CODE|137226|分号不是运算符，不能在表达式中使用。它用作JavaScript语法的一部分，用于标记被视为语句的表达式的结尾。例如，你可以说|137227|a+=+1;+b+=+2;+c+=+3;|137228|这意味着“有三个语句要按顺序执行:计算第一个表达式作为第一个语句，第二个表达式作为第二个语句，第三个表达式作为第三个语句”。|137229|在这一点上，两者并不是完全可以互换的。例如，您不能编写|137230|var+a+=+1,+var+b+=+2;|137231|因为var+a+=+1和var+b+=+2是语句，而不是表达式，因此不能用逗号分隔。在这里你必须使用分号。|137232|(注:你可以说|137233|var+a+=+1,+b+=+2;|137234|因为该语言特别允许使用逗号作为声明语句语法的一部分。在这里，逗号不用作运算符。)|137235|同样的，你也不能说|137236|a+=+(b+=+1;+c+=+2);|137237|因为在这里，表达式的右侧必须是一个表达式，而不是语句，并且使用;来分隔语句。内部的分号必须是逗号。(话又说回来，这段代码在一开始就相当笨拙和不寻常，所以您可能根本不应该这样做！)|137238|从风格的角度来看，逗号运算符很少使用，而且足够晦涩，可能会让相当称职的JavaScript程序员绊倒。因此，我强烈建议不要使用它，而是遵循JavaScript中关于使用分号终止语句的既定约定，即使使用逗号分隔每个用作语句的表达式在语法上是合法的，也是等效的。|137239|希望这能有所帮助！|137240|entityMap^0|0|0|5|5|E|5|N|5|11|5|0|0|0|0|0|0|2|9|C|9|0|0|0|0|0|0|V|1|0|0|0^^$0|@$1|2|3|4|5|6|7|1G|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|1H|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|1I|8|@$I|1J|J|1K|K|L]|$I|1L|J|1M|K|L]|$I|1N|J|1O|K|L]|$I|1P|J|1Q|K|L]]|9|@]|A|$]]|$1|M|3|N|5|6|7|1R|8|@]|9|@]|A|$]]|$1|O|3|P|5|D|7|1S|8|@]|9|@]|A|$E|F]]|$1|Q|3|R|5|6|7|1T|8|@]|9|@]|A|$]]|$1|S|3|T|5|6|7|1U|8|@]|9|@]|A|$]]|$1|U|3|V|5|D|7|1V|8|@]|9|@]|A|$E|F]]|$1|W|3|X|5|6|7|1W|8|@$I|1X|J|1Y|K|L]|$I|1Z|J|20|K|L]]|9|@]|A|$]]|$1|Y|3|Z|5|6|7|21|8|@]|9|@]|A|$]]|$1|10|3|11|5|D|7|22|8|@]|9|@]|A|$E|F]]|$1|12|3|13|5|6|7|23|8|@]|9|@]|A|$]]|$1|14|3|15|5|6|7|24|8|@]|9|@]|A|$]]|$1|16|3|17|5|D|7|25|8|@]|9|@]|A|$E|F]]|$1|18|3|19|5|6|7|26|8|@$I|27|J|28|K|L]]|9|@]|A|$]]|$1|1A|3|1B|5|6|7|29|8|@]|9|@]|A|$]]|$1|1C|3|1D|5|6|7|2A|8|@]|9|@]|A|$]]|$1|1E|3|-4|5|6|7|2B|8|@]|9|@]|A|$]]]|1F|$]]

The comma operator is an operator that can be used inside an expression. It is used to separate out multiple different expressions and has the meaning "evaluate all of the following expressions, then produce the value of the final expression." For example:

<pre><code>a = 1, b = 2, c = 3
</code></pre>

means "evaluate <code>a = 1</code>, then <code>b = 2</code>, then <code>c = 3</code>, then evaluate to the value of the expression <code>c = 3</code>.

The semicolon is not an operator and cannot be used inside an expression. It is used as part of JavaScript syntax to mark the end of an expression that is being treated as a statement. For example, you could say

<pre><code>a = 1; b = 2; c = 3;
</code></pre>

And this would mean "there are three statements to do in sequence: evaluate the first expression as the first statement, the second expression as the second statement, and the third expression as the third statement."

In this regard, the two are not completely interchangeable. For example, you cannot write

<pre><code>var a = 1, var b = 2;
</code></pre>

Because <code>var a = 1</code> and <code>var b = 2</code> are statements, not expressions, and thus can't be separated by commas. You would have to use a semicolon here. 

(A note: you could say

<pre><code>var a = 1, b = 2;
</code></pre>

because the language specifically permits this use of comma as a part of the syntax of a declaration statement. Here, comma is not used as an operator.)

Similarly, you can't say

<pre><code>a = (b = 1; c = 2);
</code></pre>

Because here the right-hand side of the expression must be an expression, not a statement, and <code>;</code> is used to separate statements. The inner semicolon would have to be a comma instead. (Then again, this code is pretty awkward and unusual in the first place, so you probably shouldn't do this at all!)

From a stylistic perspective, the comma operator is rarely used and is obscure enough that it might trip up reasonably competent JavaScript coders. As a result, I would strongly suggest not using it and instead following the established conventions in JavaScript about using semicolons to terminate statements, even if it would be equivalent and syntactically legal to use commas to separate out expressions that are each used as statements.

Hope this helps!

Given the following code:

<pre><code>var fn = function () {
 var x = 'x',
 y = 'y';
 this.a = 'a',
 this.b = 'b',
 this.c = 'c';
 this.d = 'd',
 this.e = 'e'; 
}
</code></pre>

As can be seen, there is a mix of both.

What would be the benefit of using one or the other?

My understanding is that the semicolon is to end the statement. And comma should be used to string together multiple declarations.

So is it safe to say that with this example then there should only be two semicolon?

<pre><code>var fn = function () {
 var x = 'x',
 y = 'y';
 this.a = 'a',
 this.b = 'b',
 this.c = 'c',
 this.d = 'd',
 this.e = 'e'; 
}
</code></pre>

Use of commas versus semicolons?

给定以下代码：var fn = function () {    var x = 'x',    y = 'y';    this.a = 'a',    this.b = 'b',    this.c = 'c';    this.d = 'd',    this.e = 'e';   }可以看出，两者兼而有之。使用...

问使用逗号还是分号？
EN

社区

活动

资源

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问使用逗号还是分号？EN

社区

活动

资源

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问使用逗号还是分号？
EN