blocks|key|1106281|text|非常简单，使用Math.random获取0到1之间的数字，并将其与0.02或所寻找的真/假比率进行比较。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1106282|Objects/Math/random|1106283|Math.random()函数在[0，1)范围内返回一个浮点伪随机数，即从0(包含)到但不包括1(排它)，然后可以缩放到所需的范围。
|blockquote|1106284|1106285|所以，基本上：|1106286|var+randomizer+=+function+()+{
++++return+Math.random()+>+0.02;
};|code-block|syntax|javascript|1106287|编辑|BOLD|1106288|如果您想使它更漂亮，您可以将该函数打包到一个对象中，并将其设置为true/false的比率。|1106289|var+randomizer+=+{
++++_ratio:+0.02,++//+default+ratio
++++setRatio:+function+(falses,+total)+{
++++++++this._ratio+=+falses+/+total;
++++},
++++getResult:+function+()+{
++++++++return+Math.random()+>+this._ratio;
++++}
};|1106290|然后|1106291|randomizer.getResult();+
randomizer.setRatio(60,+1000);+//+60+out+of+10000|1106292|entityMap|0|LINK|mutability|MUTABLE|url|https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/random^0|7|B|X|4|0|0|J|0|0|0|0|0|0|0|2|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|1B|8|@$9|1C|A|1D|B|C]|$9|1E|A|1F|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|1G|8|@]|D|@$9|1H|A|1I|1|1J]]|E|$]]|$1|H|3|I|5|J|7|1K|8|@]|D|@]|E|$]]|$1|K|3|-4|5|6|7|1L|8|@]|D|@]|E|$]]|$1|L|3|M|5|6|7|1M|8|@]|D|@]|E|$]]|$1|N|3|O|5|P|7|1N|8|@]|D|@]|E|$Q|R]]|$1|S|3|T|5|6|7|1O|8|@$9|1P|A|1Q|B|U]]|D|@]|E|$]]|$1|V|3|W|5|6|7|1R|8|@]|D|@]|E|$]]|$1|X|3|Y|5|P|7|1S|8|@]|D|@]|E|$Q|R]]|$1|Z|3|10|5|6|7|1T|8|@]|D|@]|E|$]]|$1|11|3|12|5|P|7|1U|8|@]|D|@]|E|$Q|R]]|$1|13|3|-4|5|6|7|1V|8|@]|D|@]|E|$]]]|14|$15|$5|16|17|18|E|$19|1A]]]]

Pretty easy, use <code>Math.random</code> to get a number between 0 and 1, and compare it to <code>0.02</code> or the rate of true/false you are looking for. 

<a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/random" rel="nofollow">https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/random</a>

<blockquote>
 The Math.random() function returns a floating-point, pseudo-random number in the range [0, 1) that is, from 0 (inclusive) up to but not including 1 (exclusive), which you can then scale to your desired range.
</blockquote>

So, basically:

<pre><code>var randomizer = function () {
 return Math.random() &gt; 0.02;
};
</code></pre>

EDIT

If you want to make it more beautiful, you can pack this function in an object, and set there the ratio of true/false.

<pre><code>var randomizer = {
 _ratio: 0.02, // default ratio
 setRatio: function (falses, total) {
 this._ratio = falses / total;
 },
 getResult: function () {
 return Math.random() &gt; this._ratio;
 }
};
</code></pre>

and then

<pre><code>randomizer.getResult(); 
randomizer.setRatio(60, 1000); // 60 out of 10000
</code></pre>

blocks|key|4117155|text|function+mostlyFalse()+{
++++return+Math.random()+<=+0.05;++++
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|4117156|jsfiddle随机显示大部分是‘真’，但偶尔出现‘假’：http://jsfiddle.net/t8E6t/1/|unstyled|offset|length|4117157|entityMap|0|LINK|mutability|MUTABLE|url|http://jsfiddle.net/t8E6t/1/^0|0|T|S|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|R|8|@]|9|@$G|S|H|T|1|U]]|A|$]]|$1|I|3|-4|5|F|7|V|8|@]|9|@]|A|$]]]|J|$K|$5|L|M|N|A|$O|P]]]]

<pre><code>function mostlyFalse() {
 return Math.random() &lt;= 0.05; 
}
</code></pre>

jsfiddle randomly showing mostly 'true's, but with the occasional 'false': <a href="http://jsfiddle.net/t8E6t/1/" rel="nofollow">http://jsfiddle.net/t8E6t/1/</a>

blocks|key|1650042|text|怎么样|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1650043|赔率:+50/1000+=+1/20|1650044|//Get+random+number+from+1+to+20,+if+equals+20+return+false
if+(Math.floor((Math.random()*20)%2B1)+==+20)
{
++return+false;
}
else{
++return+true;
}|code-block|syntax|javascript|1650045|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|L|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|M|8|@]|9|@]|A|$G|H]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

How about

Odds: 50/1000 = 1/20

<pre><code>//Get random number from 1 to 20, if equals 20 return false
if (Math.floor((Math.random()*20)+1) == 20)
{
 return false;
}
else{
 return true;
}
</code></pre>

blocks|key|4117125|text|使用Math.random，您可以实现您想要的结果：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|4117126|function+suchRandom(chanceInPercent){
++++return+Math.random()+>+chanceInPercent/100;
}

console.log(suchRandom(2));+//because+1000/50+=+20+true+/+1000+calls+=+2%25|code-block|syntax|javascript|4117127|大约20：http://jsfiddle.net/Ru7qY/1/|4117128|entityMap|0|LINK|mutability|MUTABLE|url|http://jsfiddle.net/Ru7qY/1/^0|2|B|0|0|5|S|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@$9|V|A|W|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|X|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|Y|8|@]|D|@$9|Z|A|10|1|11]]|E|$]]|$1|M|3|-4|5|6|7|12|8|@]|D|@]|E|$]]]|N|$O|$5|P|Q|R|E|$S|T]]]]

With <code>Math.random</code>, you can achieve what you want :

<pre><code>function suchRandom(chanceInPercent){
 return Math.random() &gt; chanceInPercent/100;
}

console.log(suchRandom(2)); //because 1000/50 = 20 true / 1000 calls = 2%
</code></pre>

Around 20 : <a href="http://jsfiddle.net/Ru7qY/1/" rel="nofollow">http://jsfiddle.net/Ru7qY/1/</a>

blocks|key|1106294|text|function+foo+()+{+return+Math.random()+>+0.02;+}

//+1+/+50+==+0.02,+so+if+it's+less+than+0.02+return+false|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1106295|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>function foo () { return Math.random() &gt; 0.02; }

// 1 / 50 == 0.02, so if it's less than 0.02 return false
</code></pre>

blocks|key|1650149|text|每次函数运行时，创建一个随机数，介于1到50之间：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1650150|var+num+=+Math.floor((Math.random()*50)%2B1);|code-block|syntax|javascript|1650151|然后，如果数字等于50，例如，返回false。|1650152|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|$]]

Create a random number each time the function runs, between 1 and 50:

<pre><code>var num = Math.floor((Math.random()*50)+1);
</code></pre>

Then, if the number equals 50, for example, return false.

blocks|key|4117176|text|我觉得最简洁、最简单的答案就是这个一行函数。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4117177|//+A+function+that+has+a+50%25+chance+of+returning+true+by+default
function+chance(+c+=+0.5+){
++++return+Math.random()+<+c;
}|code-block|syntax|javascript|4117178|像这样使用它|4117179|//+Block+has+a+60%25+chance+of+being+executed.
if(+chance(+.6+)+){
++++//Do+stuff
}

//+Or,+to+solve+your+problem+specifically
var+c+=+chance(+49+/+50+);|4117180|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

I feel like the most concise, simple answer is this one-liner function

<pre><code>// A function that has a 50% chance of returning true by default
function chance( c = 0.5 ){
 return Math.random() &lt; c;
}
</code></pre>

Use it like so

<pre><code>// Block has a 60% chance of being executed.
if( chance( .6 ) ){
 //Do stuff
}

// Or, to solve your problem specifically
var c = chance( 49 / 50 );
</code></pre>

blocks|key|4117146|text|柜台..。:D|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4117147|var+c+=+0;
function+f()
{
++++return+%2B%2Bc+%25+50+==+0+?+false+:+true;
}|code-block|syntax|javascript|4117148|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|$]]

counter.... :D 

<pre><code>var c = 0;
function f()
{
 return ++c % 50 == 0 ? false : true;
}
</code></pre>

I'd like to make a function that returns <code>true</code> most of the time when it's called but that will return <code>false</code> occasionally?

By occasionally I mean, at 1000 calls, it'll have an average of one <code>false</code> every 50 calls.

How to make a JavaScript function that usually returns true, but returns false randomly, once every 50 times on average?

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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我想要创建一个函数，它在调用时大部分时间返回true，但它偶尔会返回false？偶尔，我的意思是，在1000个呼叫时，平均每50个呼叫就有一个false。

问如何使通常返回true但随机返回false的JavaScript函数平均每50次返回一次？
EN

回答 8

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问如何使通常返回true但随机返回false的JavaScript函数平均每50次返回一次？EN

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问如何使通常返回true但随机返回false的JavaScript函数平均每50次返回一次？
EN