<pre class="shiki github-dark shaku"><code>/*type Callback = (error: Error, data: any) =&gt; voidtype AsyncFunc = ( callback: Callback, data: any) =&gt; void*//** * @param {AsyncFunc[]} funcs * @return {(callback: Callback) =&gt; void} */function sequence(funcs){ return function run(callback,data){ function runNext(index,data){ if(index == funcs.length){ callback(undefined,data); return; } const curFun = funcs[index]; const cb = ((e,d)=&gt;{ if(e){ callback(e,d); return; } runNext(index+1,d); }); curFun(cb,data); } runNext(0,data); }}// function sequence(funcs){// let q = [...funcs];// return function run(callback,data){// if(q.length === 0){// callback(undefined,data);// return;// }// const curFun = q.shift();// const cb = ((e,d)=&gt;{// if(e){// callback(e,d);// return;// }// run(callback,d);// });// curFun(cb,data);// }// }</code></pre>

my solution

This problem is similar to 11. what is Composition? create a pipe(). You are asked to implement an async function helper, sequence() which chains up a…