手动实现一个compose函数

Question

手动实现一个compose函数，满足以下功能：

var arr = [func1, func2, func3];
function func1 (ctx, next) {
    ctx.index++
    next();
}
function func2 (ctx, next) {
    setTimeout(function() {
        ctx.index++;
        next();
    });
}
function func3 (ctx, next) {
    console.log(ctx.index);
}
compose(arr)({index: 0}); // 输出：2

Answer 1

我之前看了个关于这个的，给你那改造了一下，看能不能给你提供点思路：

var compose = function(...args) {
    var len = args.length
    var count = len - 1
    var result
    return function f1(...args1) {
        result = args[count].apply(this, args1)
        if (count <= 0) {
            count = len - 1
            return result
        } else {
            count--
            return f1.call(null, result)
        }
    }
}

function func1 (ctx) {
    return ++ctx.index;

}
function func2 (ctx) {
   return ++ctx;

}
function func3 (ctx) {
    console.log(ctx);
}

compose(func3,func2,func1)({index : 1});

Answer 2

const compose = (arr) => {
  return function(ctx) {
    [...arr].reverse().reduce((func, item) => {
      return function(ctx) {
        item(ctx, function() {
          func(ctx)
        })
      }
    }, ()=>{})(ctx)
  }
}

反人类版本我也会！

const compose = arr => ctx => [...arr].reverse().reduce((func, item) => ctx => item(ctx, () => func(ctx)), () => {})(ctx)

Answer 3

var arr = [func1, func2, func3];
function func1 (ctx, next) {
    ctx.index++
    next();
}
function func2 (ctx, next) {
    setTimeout(function() {
        ctx.index++;
        next();
    });
}
function func3 (ctx, next) {
    console.log(ctx.index);
}
        
const compose = (arr) => (ctx) => {
    const promise = new Promise((resolve,reject)=>{
        func1(ctx,resolve)
    });
    promise.then(()=>{
        return new Promise((resolve,reject)=>{
            func2(ctx,resolve)
        });
    }).then(()=>{
        return new Promise((resolve,reject)=>{
            func3(ctx)
        });
    }).catch(e=>console.log(e));
};

        
        
compose(arr)({index: 0});

还可以写的再反人类1点

const compose = (arr) => (ctx) => new Promise((resolve,reject)=>{func1(ctx,resolve)}).then(()=>new Promise((resolve,reject)=>{func2(ctx,resolve)})).then(()=>new Promise((resolve,reject)=>{func3(ctx)})).catch(e=>console.log(e));