js中Compose函数实现扁平化

// 将前一个函数的结果作为初始值带入下一个函数中，实现函数的扁平化

function compose(...funcs) {
    
     //...func为传入的函数
    return function proxy(...args) {
    
    //...args为第一次调用函数所传入的参数
        let len = funcs.length;
        if (len === 0) {
    
    
            return args;
        } else if (len === 1) {
    
    
            return funcs[0](...args);
        } else {
    
    
            return funcs.reduce((x, y) => {
    
    
                return typeof x === "function" ? y(x(...args)) : y(x)
            });
        }
    }
}
let fn1 = function (x) {
    
    
    return x + 10;
};
let fn2 = function (x) {
    
    
    return x * 10;
};
let fn3 = function (x) {
    
    
    return x / 10;
};
console.log(compose()(5));  //5
console.log(compose(fn1)(5)); //15
console.log(compose(fn1, fn2)(5));  //150 
console.log(compose(fn1, fn2, fn1, fn3)(5)); //16

// redux中的compose源码
function compose(...funcs){
    
    
    if(funcs.length===0){
    
    
        return arg=>arg;
    }
    if(funcs.length===1){
    
    
        return funcs[0];
    }
    return funcs.reduce((a,b)=>(...args)=>a(b(...args)));
}
console.log(compose()(5));  //5
console.log(compose(fn1)(5)); //15
console.log(compose(fn1, fn2)(5));  //60
console.log(compose(fn1, fn2, fn1, fn3)(5)); //115