blocks|key|2522717|text|您将一个数组传递给compose，而不是传递给一个函数(或多个函数)，因此fn是一个数组，当您尝试将其用作函数时，您会得到该错误。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2522718|将...fns替换为fns+(这样compose需要一个数组)，或者删除调用中的方括号以进行compose。还要使用您已注释掉的func3版本：|2522719|​|2522720|const+compose+=+(...fns)+=>+(...args)+=>
++++++fns.reduceRight((acc,+fn)+=>+fn(acc),+args);

const+func3+=+([x,+y])+=>+(y+>+0+?+x+%2B+3+:+x+-+3);

const+func2+=+x+=>+x+**+2;

const+func1+=+x+=>+x+-+8;

const+fnOne+=+compose(func1,+func2,+func3)('3',+1);
console.log(fnOne);+//+should+be+1081

const+fnTwo+=+compose(func1,+func2,+func3)('3',+-1);
console.log(fnTwo);+//should+be+-8|code-block|syntax|javascript|2522721|2522722|entityMap^0|11|2|0|1|6|A|3|0|0|0|0^^$0|@$1|2|3|4|5|6|7|R|8|@$9|S|A|T|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|U|8|@$9|V|A|W|B|C]|$9|X|A|Y|B|C]]|D|@]|E|$]]|$1|H|3|I|5|6|7|Z|8|@]|D|@]|E|$]]|$1|J|3|K|5|L|7|10|8|@]|D|@]|E|$M|N]]|$1|O|3|I|5|6|7|11|8|@]|D|@]|E|$]]|$1|P|3|-4|5|6|7|12|8|@]|D|@]|E|$]]]|Q|$]]

<p>You're passing an array into compose instead of a function (or multiple functions), so <code>fn</code> is an array and you get that error when you try to use it as a function.</p>

<p>Either replace <code>...fns</code> with <code>fns</code> (so that compose expects an array) or remove the square brackets in your calls to compose. Also use the version of func3 that you have commented out:</p>

<p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
<div class="snippet-code">
<pre class="snippet-code-js lang-js prettyprint-override"><code>const compose = (...fns) =&gt; (...args) =&gt;
      fns.reduceRight((acc, fn) =&gt; fn(acc), args);

const func3 = ([x, y]) =&gt; (y &gt; 0 ? x + 3 : x - 3);

const func2 = x =&gt; x ** 2;

const func1 = x =&gt; x - 8;

const fnOne = compose(func1, func2, func3)('3', 1);
console.log(fnOne); // should be 1081

const fnTwo = compose(func1, func2, func3)('3', -1);
console.log(fnTwo); //should be -8</code></pre>
</div>
</div>
</p>


blocks|key|2523287|text|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2523288|您需要提供三个参数/函数来组成函数，而不是数组。|ordered-list-item|2523289|func3将是第一个执行的函数，因此它将接收数组参数。此数组需要在x和y变量中为destructure。此缩减可以在参数定义中进行，如下所示：(x，y)。|offset|length|2523290|2523291|​|2523292|const+compose+=+(...fns)+=>+(...args)+=>
fns.reduceRight((acc,+fn)+=>+fn(acc),+args);

const+func3+=+([x,+y])+=>+y+>+0+?+x+%2B+3+:+x+-+3;

const+func2+=+x+=>+x+**+2;

const+func1+=+x+=>+x+-+8;

const+fnOne+=+compose(func1,+func2,+func3)('3',+1);
console.log(fnOne);+//+should+be+1081

const+fnTwo+=+compose(func1,+func2,+func3)('3',+-1);
console.log(fnTwo);+//should+be+-8|code-block|syntax|javascript|2523293|2523294|entityMap|0|LINK|mutability|MUTABLE|url|https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Destructuring_assignment^0|0|0|14|B|0|0|0|0|0|0^^$0|@$1|2|3|-4|4|5|6|Y|7|@]|8|@]|9|$]]|$1|A|3|B|4|C|6|Z|7|@]|8|@]|9|$]]|$1|D|3|E|4|C|6|10|7|@]|8|@$F|11|G|12|1|13]]|9|$]]|$1|H|3|-4|4|5|6|14|7|@]|8|@]|9|$]]|$1|I|3|J|4|5|6|15|7|@]|8|@]|9|$]]|$1|K|3|L|4|M|6|16|7|@]|8|@]|9|$N|O]]|$1|P|3|J|4|5|6|17|7|@]|8|@]|9|$]]|$1|Q|3|-4|4|5|6|18|7|@]|8|@]|9|$]]]|R|$S|$4|T|U|V|9|$W|X]]]]

<ol>
<li>You need provide to compose function three parameters/function instead a array.</li>
<li>func3 will be the first function performed, so it will receive the array args. This array need be <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Destructuring_assignment" rel="nofollow noreferrer">destructure</a> in x and y variable. This reduce can be make in the parameters definition, like this: ([x, y]).</li>
</ol>

<p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
<div class="snippet-code">
<pre class="snippet-code-js lang-js prettyprint-override"><code>const compose = (...fns) =&gt; (...args) =&gt;
fns.reduceRight((acc, fn) =&gt; fn(acc), args);

const func3 = ([x, y]) =&gt; y &gt; 0 ? x + 3 : x - 3;

const func2 = x =&gt; x ** 2;

const func1 = x =&gt; x - 8;

const fnOne = compose(func1, func2, func3)('3', 1);
console.log(fnOne); // should be 1081

const fnTwo = compose(func1, func2, func3)('3', -1);
console.log(fnTwo); //should be -8</code></pre>
</div>
</div>
</p>


blocks|key|2311734|text|如果你不这样做，你可以或者想把func3转换成一个单参数函数。您可以在调用fn时扩展args。然后将结果捕获到一个数组中，以便在下一次fn调用中传播。当返回最终结果时，只需获取结果数组的第一个元素。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2311735|​|2311736|const+compose+=+(...fns)+=>+(...args)+=>
++fns.reduceRight((args,+fn)+=>+[fn(...args)],+args)[0];

const+func3+=+(x,+y)+=>+(y+>+0+?+x+%2B+3+:+x+-+3);
//+const+func3+=+([x,+y])+=>+(y+>+0+?+x+%2B+3+:+x+-+3);+-+avoid+using+this+version

const+func2+=+x+=>+x+**+2;
const+func1+=+x+=>+x+-+8;

const+fnOne+=+compose(func1,+func2,+func3)('3',+1);
console.log(fnOne);+//+should+be+1081

const+fnTwo+=+compose(func1,+func2,+func3)('3',+-1);
console.log(fnTwo);+//should+be+-8|code-block|syntax|javascript|2311737|2311738|entityMap^0|F|5|11|2|16|4|1V|2|0|0|0|0^^$0|@$1|2|3|4|5|6|7|P|8|@$9|Q|A|R|B|C]|$9|S|A|T|B|C]|$9|U|A|V|B|C]|$9|W|A|X|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|Y|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|Z|8|@]|D|@]|E|$K|L]]|$1|M|3|G|5|6|7|10|8|@]|D|@]|E|$]]|$1|N|3|-4|5|6|7|11|8|@]|D|@]|E|$]]]|O|$]]

<p>If you don't can or want to convert <code>func3</code> to a single argument function. You could spread the <code>args</code> when calling <code>fn</code>. Then capture the result in an array so it can be spread over the next <code>fn</code> call. When returning the final result simply take the first element of the resulting array.</p>

<p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
<div class="snippet-code">
<pre class="snippet-code-js lang-js prettyprint-override"><code>const compose = (...fns) =&gt; (...args) =&gt;
  fns.reduceRight((args, fn) =&gt; [fn(...args)], args)[0];

const func3 = (x, y) =&gt; (y &gt; 0 ? x + 3 : x - 3);
// const func3 = ([x, y]) =&gt; (y &gt; 0 ? x + 3 : x - 3); - avoid using this version

const func2 = x =&gt; x ** 2;
const func1 = x =&gt; x - 8;

const fnOne = compose(func1, func2, func3)('3', 1);
console.log(fnOne); // should be 1081

const fnTwo = compose(func1, func2, func3)('3', -1);
console.log(fnTwo); //should be -8</code></pre>
</div>
</div>
</p>


<p>I am trying to implement function composition with multiple arguments using reduceRight. This question has been answered at this <a href="https://stackoverflow.com/questions/55842990/multiple-arguments-composible-function-implementation-using-reduceright">link</a> but slightly with a different input data. For some reason I am getting the following error : <code>Uncaught TypeError: fn is not a function</code>. Avoid using <code>func3 = ([x, y]) =&gt; (y &gt; 0 ? x + 3 : x - 3);</code> in this format. Let me know if there is a way to fix it.</p>

<pre><code> const compose = (...fns) =&gt; (...args) =&gt;
      fns.reduceRight((acc, fn) =&gt; fn(acc), args);

    const func3 = (x, y) =&gt; (y &gt; 0 ? x + 3 : x - 3);
  //const func3 = ([x, y]) =&gt; (y &gt; 0 ? x + 3 : x - 3); - avoid using this version

    const func2 = x =&gt; x ** 2;

    const func1 = x =&gt; x - 8;

    const fnOne = compose([func1, func2, func3])('3', 1);
    console.log(fnOne); // should be 1081

    const fnTwo = compose([func1, func2, func3])('3', -1);
    console.log(fnTwo); //should be -8


  [1]: https://stackoverflow.com/questions/55842990/multiple-arguments-composible-function-implementation-using-reduceright
</code></pre>

<p><strong>SOLUTION</strong></p>

<p>Array#reduceRight only has support for one currentValue so we can't have a function accept multiple arguments. The only way would be to avoid using reduceRight for the first call by popping it from the array and calling it manual instead of letting reduceRight do it:</p>

<p><em>First approach</em> </p>

<pre><code>const compose = fns =&gt; (...args) =&gt;
      fns.reduceRight((acc, fn) =&gt; fn(acc), fns.pop()(...args));
</code></pre>

<p><em>Second approach</em></p>

<pre><code>const compose = fns =&gt; (...args) =&gt;
      fns.reduceRight((acc, fn) =&gt; fn(...[acc, ...args.slice(1)]), args[0]);
</code></pre>


Function composition with multiple arguments using reduceRight() - JavaScript

我正在尝试使用reduceRight实现具有多个参数的函数组合。这个问题已经在这个上得到了回答，但使用的输入数据略有不同。由于某种原因，我得到了以下错误：Uncaught TypeError: fn is not a function。避免使用这种格式的func3 = ([x, y]) => (y > 0 ? x + ...

问使用reduceRight() - JavaScript组合具有多个参数的函数
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