blocks|key|1203879|text|这是一个函数，用于检查是否可以使用yield。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1203880|var+can_yield+=+(function(){+
++++try+{+
++++++++return+eval("!!Function('yield+true;')().next()");+
++++}+
++++catch(e)+{+
++++++++return+false;+
++++}+
})();|code-block|syntax|javascript|1203881|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Here's a function for checking if yield can be used.

<pre><code>var can_yield = (function(){ 
 try { 
 return eval("!!Function('yield true;')().next()"); 
 } 
 catch(e) { 
 return false; 
 } 
})();
</code></pre>

blocks|key|2613397|text|yield为JavaScript引入了新的语法。除非通过在script+type属性(*)中包含版本号来指定要使用新的JavaScript语法，否则将无法使用yield。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2613398|指定脚本版本时，只有支持给定版本的浏览器才会执行该块。因此，只有火狐，而不是IE、Opera或WebKit，才会在以下代码中执行顶部代码块：|2613399|<script+type="text/javascript;version=1.7">
++++function+x()+{
++++++++yield+0;
++++}
++++var+canyield=+true;
</script>
<script+type="text/javascript">
++++if+(!window.canyield)+{
++++++++//+do+some+fallback+for+other+browsers
++++}
</script>|code-block|syntax|javascript|2613400|(*：请注意，type属性中指定的类型和版本专门决定是否获取和执行外部脚本，以及执行的模式。不幸的是，脚本的Content-Type被完全忽略了。)|2613401|entityMap^0|0|5|T|B|27|5|0|0|0|7|4|1I|C|0^^$0|@$1|2|3|4|5|6|7|Q|8|@$9|R|A|S|B|C]|$9|T|A|U|B|C]|$9|V|A|W|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|X|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|Y|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|Z|8|@$9|10|A|11|B|C]|$9|12|A|13|B|C]]|D|@]|E|$]]|$1|O|3|-4|5|6|7|14|8|@]|D|@]|E|$]]]|P|$]]

<code>yield</code> introduces new syntax to JavaScript. You won't be able to use <code>yield</code> unless you have specified that you want the new JavaScript syntax, by including a version number in the <code>script type</code> attribute(*).

When you specify a script version, only browsers that support the given version will execute the block at all. So only Firefox, and not IE, Opera or WebKit, will execute the top block in:

<pre><code>&lt;script type="text/javascript;version=1.7"&gt;
 function x() {
 yield 0;
 }
 var canyield= true;
&lt;/script&gt;
&lt;script type="text/javascript"&gt;
 if (!window.canyield) {
 // do some fallback for other browsers
 }
&lt;/script&gt;
</code></pre>

(*: note that the type and version specified in the <code>type</code> attribute exclusively determines whether external scripts are fetched, executed, and the mode for the execution. The <code>Content-Type</code> of a script is, unfortunately, completely ignored.)

blocks|key|869022|text|这是我对检查原生yield支持的看法。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|869023|var+canYield+=+(function(){try{yield;}catch(e){}}())!==undefined;|code-block|syntax|javascript|869024|现代化测试|BOLD|869025|define(['Modernizr'],+function(+Modernizr+)+{
++//+native+yield+support.
++Modernizr.addTest('yield',+(function(){try{yield;}catch(e){}}())!==undefined);
});|869026|Performance+http://jsperf.com/yield-support|869027|📷|atomic|869028|869029|​|869030|entityMap|0|LINK|mutability|MUTABLE|url|http://jsperf.com/yield-support|1|IMAGE|IMMUTABLE|imageUrl|https://ask.qcloudimg.com/http-save/yehe-900000/25d97f85e7583ef1eea38e23ee74b561.png|imageAlt|2|https://i.stack.imgur.com/dMYyw.png^0|8|5|0|0|0|5|0|0|0|B|C|V|0|0|0|1|1|0|0|1|2|0|0^^$0|@$1|2|3|4|5|6|7|1D|8|@$9|1E|A|1F|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|1G|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|1H|8|@$9|1I|A|1J|B|M]]|D|@]|E|$]]|$1|N|3|O|5|H|7|1K|8|@]|D|@]|E|$I|J]]|$1|P|3|Q|5|6|7|1L|8|@$9|1M|A|1N|B|M]]|D|@$9|1O|A|1P|1|1Q]]|E|$]]|$1|R|3|S|5|T|7|1R|8|@]|D|@$9|1S|A|1T|1|1U]]|E|$]]|$1|U|3|S|5|T|7|1V|8|@]|D|@$9|1W|A|1X|1|1Y]]|E|$]]|$1|V|3|W|5|6|7|1Z|8|@]|D|@]|E|$]]|$1|X|3|-4|5|6|7|20|8|@]|D|@]|E|$]]]|Y|$Z|$5|10|11|12|E|$13|14]]|15|$5|16|11|17|E|$18|19|1A|-4]]|1B|$5|16|11|17|E|$18|1C|1A|-4]]]]

Here's my take on checking for native <code>yield</code> support.

<pre><code>var canYield = (function(){try{yield;}catch(e){}}())!==undefined;
</code></pre>

Modernizr test

<pre><code>define(['Modernizr'], function( Modernizr ) {
 // native yield support.
 Modernizr.addTest('yield', (function(){try{yield;}catch(e){}}())!==undefined);
});
</code></pre>

Performance
<a href="http://jsperf.com/yield-support" rel="noreferrer">http://jsperf.com/yield-support</a>
<img src="https://i.stack.imgur.com/9Dfpw.png" alt="enter image description here">
<img src="https://i.stack.imgur.com/dMYyw.png" alt="enter image description here">

blocks|key|121629|text|严格地说，只有Mozilla浏览器支持JavaScript。所有浏览器都应该支持ECMAScript，旧版本的JavaScript是ECMAScript的实现。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|121630|This+site列出了哪些版本的浏览器支持哪些版本的Javascript。|offset|length|121631|MSIE使用JScript。JScript在其中没有yield。因此，使用yield将限制浏览器对页面的支持。|121632|有关使用JavaScript+1.7的信息，请尝试使用https://developer.mozilla.org/en/New_in_JavaScript_1.7|121633|entityMap|0|LINK|mutability|MUTABLE|url|http://ejohn.org/blog/versions-of-javascript/|1|https://developer.mozilla.org/en/New_in_JavaScript_1.7^0|0|0|9|0|0|0|R|1I|1|0^^$0|@$1|2|3|4|5|6|7|T|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|U|8|@]|9|@$D|V|E|W|1|X]]|A|$]]|$1|F|3|G|5|6|7|Y|8|@]|9|@]|A|$]]|$1|H|3|I|5|6|7|Z|8|@]|9|@$D|10|E|11|1|12]]|A|$]]|$1|J|3|-4|5|6|7|13|8|@]|9|@]|A|$]]]|K|$L|$5|M|N|O|A|$P|Q]]|R|$5|M|N|O|A|$P|S]]]]

Strictly speaking, only Mozilla Browsers support JavaScript. All browsers should support ECMAScript and older versions of JavaScript are implementations of ECMAScript.

<a href="http://ejohn.org/blog/versions-of-javascript/" rel="noreferrer">This site</a> lists what versions of Javascript are supported on what versions of browser.

MSIE uses JScript. JScript does not have yield in it. Therefore, using yield will limit the browser support for your page.

Try <a href="https://developer.mozilla.org/en/New_in_JavaScript_1.7" rel="noreferrer">https://developer.mozilla.org/en/New_in_JavaScript_1.7</a> for info on using JavaScript 1.7

blocks|key|869068|text|我最近花了很多时间使用yield，博本斯并不是完全错了，但Chrome31无法将JavaScript版本解释为1.7块，即使打开了实验标志(+Chrome+://+JavaScript+/#enable-javascript-harmony)。由于Chrome31和火狐之间的实现差异，Tymon+Sturgeon的方法无法在实验JS打开的Chrome31中检测到yield，尽管它非常接近。只需稍加修改，它就可以检测火狐和Chrome31的yield是否存在。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|869069|首先，我将快速介绍一下yield的不同之处(为了清楚起见，我写了很长一段时间)：|869070|在Firefox中：|869071|var+fooGen+=+function(){+yield+1;+yield+2;+};
var+iterator+=+fooGen();
console.log(iterator.next());++++//+prints+1
console.log(iterator.next());++++//+prints+2|code-block|syntax|javascript|869072|在启用了实验JavaScript的Chrome+31中：|869073|//+Note+the+*
var+fooGen+=+function*(){+yield+1;+yield+2;+};
var+iterator+=+fooGen();
console.log(iterator.next().value);++++//+prints+1
console.log(iterator.next().value);++++//+prints+2|869074|.value在Chrome中是必需的，因为它产生一个对象，但更重要的是，生成器在函数定义中需要一个"*“。此外，我也找不到一种方法来从大写的"F“函数创建一个生成器:+Chrome中的new+Function('',+'{yield+5;}');。如果你知道怎么做，请在下面留言。|869075|为了正确地检测火狐和Chrome中的yield，我使用了一些来回的代码：|869076|<script+type="application/javascript">
++++var+can_yield+=+(function(){+
++++++++try+{
++++++++++++//+Assuming+Chrome's+generator+syntax
++++++++++++var+funcUsingYield+=+new+Function('',+'{+var+interp+=+function*+generator(){+yield+true;+}}');
++++++++++++return+true;
++++++++}+catch(e)+{+
++++++++++++return+false;+
++++++++}+
++++})();
</script>

<script+type="application/javascript;version=1.7">
++++//+Redefine+the+`can_yield`+function+inside+a+JS1.7+block.+Probably+safe+to+simply+return+true
++++can_yield+=+(function(){+
++++++++try+{+
++++++++++++return+eval("!!Function('yield+true;')().next()");+
++++++++}+
++++++++catch(e)+{+
++++++++++++return+false;+
++++++++}+
++++})();
</script>

<script+type="application/javascript">
++++if(!can_yield)
++++{
++++++++alert("Can't+Yield!");
++++}
</script>|869077|测试时间：|869078|869079|Firefox+25：yield+works|unordered-list-item|BOLD|869080|Chrome+31与实验JS+On：yield+works|869081|Chrome+31与实验JS+关闭：<代码>D28不工作<代码>H229<代码>H130和<代码>E131E232：<代码>D33不工作<代码>H234<代码>F235|869082|869083|entityMap^0|B|5|52|5|65|5|0|B|5|0|0|0|0|0|0|6|2K|V|0|I|5|0|0|0|0|0|A|B|5|0|0|9|F|2|I|5|0|0|9|F|2|0|0^^$0|@$1|2|3|4|5|6|7|1C|8|@$9|1D|A|1E|B|C]|$9|1F|A|1G|B|C]|$9|1H|A|1I|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|1J|8|@$9|1K|A|1L|B|C]]|D|@]|E|$]]|$1|H|3|I|5|6|7|1M|8|@]|D|@]|E|$]]|$1|J|3|K|5|L|7|1N|8|@]|D|@]|E|$M|N]]|$1|O|3|P|5|6|7|1O|8|@]|D|@]|E|$]]|$1|Q|3|R|5|L|7|1P|8|@]|D|@]|E|$M|N]]|$1|S|3|T|5|6|7|1Q|8|@$9|1R|A|1S|B|C]|$9|1T|A|1U|B|C]]|D|@]|E|$]]|$1|U|3|V|5|6|7|1V|8|@$9|1W|A|1X|B|C]]|D|@]|E|$]]|$1|W|3|X|5|L|7|1Y|8|@]|D|@]|E|$M|N]]|$1|Y|3|Z|5|6|7|1Z|8|@]|D|@]|E|$]]|$1|10|3|-4|5|6|7|20|8|@]|D|@]|E|$]]|$1|11|3|12|5|13|7|21|8|@$9|22|A|23|B|14]|$9|24|A|25|B|C]]|D|@]|E|$]]|$1|15|3|16|5|13|7|26|8|@$9|27|A|28|B|14]|$9|29|A|2A|B|14]|$9|2B|A|2C|B|C]]|D|@]|E|$]]|$1|17|3|18|5|13|7|2D|8|@$9|2E|A|2F|B|14]|$9|2G|A|2H|B|14]]|D|@]|E|$]]|$1|19|3|-4|5|6|7|2I|8|@]|D|@]|E|$]]|$1|1A|3|-4|5|6|7|2J|8|@]|D|@]|E|$]]]|1B|$]]

I have spent a lot of time with <code>yield</code> recently, and bobince isn't completely wrong, but Chrome 31 does not interpret JavaScript version to 1.7 blocks, even with the Experimental JavaScript flag turned on (chrome://flags/#enable-javascript-harmony). Due to implementation differences between Chrome 31 and Firefox, Tymon Sturgeon's method is unable to detect <code>yield</code> in Chrome 31 with Experimental JS on, although it is very close. With a few modifications, it can detect the existence of <code>yield</code> for both Firefox and Chrome 31 with Experimental JS on.

First I'll quickly cover the <code>yield</code> differences (writing it the long way for clarity):

In Firefox:

<pre><code>var fooGen = function(){ yield 1; yield 2; };
var iterator = fooGen();
console.log(iterator.next()); // prints 1
console.log(iterator.next()); // prints 2
</code></pre>

In Chrome 31 with Experimental JavaScript enabled:

<pre><code>// Note the *
var fooGen = function*(){ yield 1; yield 2; };
var iterator = fooGen();
console.log(iterator.next().value); // prints 1
console.log(iterator.next().value); // prints 2
</code></pre>

<code>.value</code> is required in Chrome because it yields an object, but more importantly, the generator requires a "*" in the function definition. Also, I could not find a way to create a generator from the capital "F" Function: <code>new Function('', '{yield 5;}');</code> in Chrome. If you know how, leave a comment below.

To properly detect <code>yield</code> in Firefox and Chrome, I have used a bit of code with some back and forth:

<pre><code>&lt;script type="application/javascript"&gt;
 var can_yield = (function(){ 
 try {
 // Assuming Chrome's generator syntax
 var funcUsingYield = new Function('', '{ var interp = function* generator(){ yield true; }}');
 return true;
 } catch(e) { 
 return false; 
 } 
 })();
&lt;/script&gt;

&lt;script type="application/javascript;version=1.7"&gt;
 // Redefine the `can_yield` function inside a JS1.7 block. Probably safe to simply return true
 can_yield = (function(){ 
 try { 
 return eval("!!Function('yield true;')().next()"); 
 } 
 catch(e) { 
 return false; 
 } 
 })();
&lt;/script&gt;

&lt;script type="application/javascript"&gt;
 if(!can_yield)
 {
 alert("Can't Yield!");
 }
&lt;/script&gt;
</code></pre>

Tested in:

<ul>
<li>Firefox 25: <code>yield</code> works</li>
<li>Chrome 31 with Experimental JS On: <code>yield</code> works</li>
<li>Chrome 31 with Experimental JS Off: <code>yield</code> does not work</li>
<li>and IE10: <code>yield</code> does not work</li>
</ul>

blocks|key|1203930|text|在注意到skulpt也做了同样的事情之后，我们实际上在“纯javascript”中实现了“that”，也就是没有使用FIREFOX的“that”。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1203931|从理论上讲，完全相同的事情可以手动完成(即，通过遵循如何将函数转换为生成器的规则，费力地手工编写翻译后的函数)，或者通过javascript-+to+-javascript语言翻译器运行javascript+(!)|1203932|要实现这样的"Beast“，您必须使函数能够跳到它最后一次”退出“的位置(通过that语句)。因此，所有变量都必须存储在临时状态(!)并且代码执行相应地改变，以接受该临时状态信息。这包括while语句、for循环以及"if“语句。|1203933|这是可以做到的。|1203934|..。但这只是一项苦差事:你需要有效地编写一个完整的编译器来解析任何javascript程序，然后对其进行“转换”，然后输出修改后的javascript。|1203935|我。|1203936|entityMap^0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|O|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|P|8|@]|9|@]|A|$]]|$1|F|3|G|5|6|7|Q|8|@]|9|@]|A|$]]|$1|H|3|I|5|6|7|R|8|@]|9|@]|A|$]]|$1|J|3|K|5|6|7|S|8|@]|9|@]|A|$]]|$1|L|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|M|$]]

we actually implemented "yield", programmatically, in "pure javascript" i.e. WITHOUT USING FIREFOX "yield", for pyjamas, after noting that skulpt also had done likewise.

in theory, the exact same thing could be done either manually (i.e. by laboriously hand-coding a translated function by following the rules on how to turn a function into a generator) or by running javascript through a javascript-to-javascript language translator (!)

what's required to implement such a "Beast" is that you have to make the function capable of skipping up to the point where it was last "exited" (by a yield statement). thus, all variables must be stored in temporary state (!) and the code-execution altered accordingly, to accept this temporary state-info. that includes while statements, for loops as well as "if" statements.

it can be done...

... but it's just a bitch of a job: you need, effectively to write an entire compiler that parses any javascript program, then "transforms" it, and then outputs the modified javascript.

l.

blocks|key|121676|text|实际上，你可以使用一些技术，但我怀疑这些技术是否有任何真正的价值|type|unstyled|depth|inlineStyleRanges|entityRanges|data|121677|(function+test_key_word(keyword){
var+wrong+=+false;
try+{
++++eval(keyword+%2B+"=42");
}+
catch(e)+{
++++wrong+=+true;
}+finally+{
++++if+(wrong)+{+return+"definitely+wrong"+}
++++else+
++++if+(window[keyword]+!==+42)+{
++++++++return+"very+probably,+wrong"
++++}
++++else+{
++++++++return+"can+be+acceptable,+but+nevertheless+i+wouldn't+rely+upon+such+tests"
++++}
}})("in")|code-block|syntax|javascript|121678|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

whell, actually there are some techniques you can use, but I doubt such techniques have any real value

<pre><code>(function test_key_word(keyword){
var wrong = false;
try {
 eval(keyword + "=42");
} 
catch(e) {
 wrong = true;
} finally {
 if (wrong) { return "definitely wrong" }
 else 
 if (window[keyword] !== 42) {
 return "very probably, wrong"
 }
 else {
 return "can be acceptable, but nevertheless i wouldn't rely upon such tests"
 }
}})("in")
</code></pre>

I read about the yield keyword in JavaScript and I need to use it in my project. I read that this keyword has been implemented starting from a certain version of JS so I think that old browsers don't support it (right?).

Is there a way to check if the yield keyword is supported? or at least is there a way to check if the version of JS is greater or equal than the one that implements that keyword (1.7)?

Javascript check yield support

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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我在JavaScript中读到了read关键字，我需要在我的项目中使用它。我读到这个关键字是从JS的某个版本开始实现的，所以我认为旧的浏览器不支持它(对吧？)。有没有办法检查yield关键字是否受支持？或者至少有一种方法可以检查JS的版本是否高于或等于实现该关键字的版本(1.7)？

问Javascript check yield支持
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回答 7

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问Javascript check yield支持EN

回答 7

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问Javascript check yield支持
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