2632-Curry.js

// 2632. Curry
// Given a function fn, return a curried version of that function.
// A curried function is a function that accepts fewer or an equal number of parameters as the original function and returns either another curried function or the same value the original function would have returned.
// In practical terms, if you called the original function like sum(1,2,3), you would call the curried version like csum(1)(2)(3), csum(1)(2,3), csum(1,2)(3), or csum(1,2,3). 
// All these methods of calling the curried function should return the same value as the original.

// Example 1:
// Input: 
// fn = function sum(a, b, c) { return a + b + c; }
// inputs = [[1],[2],[3]]
// Output: 6
// Explanation:
// The code being executed is:
// const curriedSum = curry(fn);
// curriedSum(1)(2)(3) === 6;
// curriedSum(1)(2)(3) should return the same value as sum(1, 2, 3).

// Example 2:
// Input:
// fn = function sum(a, b, c) { return a + b + c; }
// inputs = [[1,2],[3]]
// Output: 6
// Explanation:
// curriedSum(1, 2)(3) should return the same value as sum(1, 2, 3).

// Example 3:
// Input:
// fn = function sum(a, b, c) { return a + b + c; }
// inputs = [[],[],[1,2,3]]
// Output: 6
// Explanation:
// You should be able to pass the parameters in any way, including all at once or none at all.
// curriedSum()()(1, 2, 3) should return the same value as sum(1, 2, 3).

// Example 4:
// Input:
// fn = function life() { return 42; }
// inputs = [[]]
// Output: 42
// Explanation:
// currying a function that accepts zero parameters should effectively do nothing.
// curriedLife() === 42
 
// Constraints:
//         1 <= inputs.length <= 1000
//         0 <= inputs[i][j] <= 10^5
//         0 <= fn.length <= 1000
//         inputs.flat().length == fn.length
//         function parameters explicitly defined
//         If fn.length > 0 then the last array in inputs is not empty
//         If fn.length === 0 then inputs.length === 1 

/**
 * @param {Function} fn
 * @return {Function}
 */
var curry = function(fn) {
    return function curried(...args) {
        // 参数够了就返回结果
		if(args.length >= fn.length) {
            return fn(...args);
        }
        // 参数不够返回,接收剩余参数的函数 (...args, ...nextArgs) 是关键
        return (...nextArgs) => curried(...args, ...nextArgs);
    }
};

/**
 * function sum(a, b) { return a + b; }
 * const csum = curry(sum);
 * csum(1)(2) // 3
 */

// Example 1:
let fn = function sum(a, b, c) { return a + b + c; }
const curriedSum = curry(fn);
console.log(fn);
console.log(curriedSum(1)(2)(3)); // 6

// Example 2:
console.log(curriedSum(1, 2)(3)); // 6

// Example 3:
console.log(curriedSum()()(1, 2, 3) ); // 6

// Example 4:
fn = function life() { return 42; }
const curriedLife = curry(fn);
console.log(fn);
console.log(curriedLife()); // 42