Javascript 可变咖喱求和函数
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Variadic curried sum function
提问by Yaroslav Yakovlev
I need a js sum function to work like this:
我需要一个 js sum 函数才能像这样工作：
sum(1)(2) = 3
sum(1)(2)(3) = 6
sum(1)(2)(3)(4) = 10
etc.
I heard it can't be done. But heard that if adding +in front of sumcan be done.
Like +sum(1)(2)(3)(4).
Any ideas of how to do this?
听说做不到 不过听说如果+在前面加上sum就可以了。喜欢+sum(1)(2)(3)(4)。
关于如何做到这一点的任何想法？
回答by Rafael
回答by yury.hrynko
This is an example of using empty brackets in the last call as a close key (from my last interview):
这是在最后一次调用中使用空括号作为关闭键的示例（来自我上次采访）：
sum(1)(4)(66)(35)(3)()
总和(1)(4)(66)(35)(3)()
function sum(numberOne) {
var count = numberOne;
return function by(numberTwo) {
if (numberTwo === undefined) {
return count;
} else {
count += numberTwo;
return by;
}
}
}
console.log(sum(1)(4)(66)(35)(3)());回答by Brad
I'm posting this revision as its own post since I apparently don't have enough reputation yet to just leave it as a comment. This is a revision of @Rafael 's excellent solution.
我将此修订版作为自己的帖子发布，因为我显然还没有足够的声誉来将其作为评论。这是@Rafael 优秀解决方案的修订版。
function sum (n) {
var v = x => sum (n + x);
v.valueOf = () => n;
return v;
}
console.log(+sum(1)(2)(3)(4)); //10
I didn't see a reason to keep the v.toString bit, as it didn't seem necessary. If I erred in doing so, please let me know in the comments why v.toString is required (it passed my tests fine without it). Converted the rest of the anonymous functions to arrow functions for ease of reading.
我没有看到保留 v.toString 位的理由，因为它似乎没有必要。如果我这样做是错误的，请在评论中告诉我为什么需要 v.toString（没有它它通过了我的测试）。将其余的匿名函数转换为箭头函数以方便阅读。
回答by Artokun
Here is a solution that uses ES6 and toString, similar to @Vemba
这是一个使用 ES6 和 的解决方案toString，类似于@Vemba
function add(a) {
let curry = (b) => {
a += b
return curry
}
curry.toString = () => a
return curry
}
console.log(add(1))
console.log(add(1)(2))
console.log(add(1)(2)(3))
console.log(add(1)(2)(3)(4))回答by user1034533
Here's a solution with a generic variadic curry function in ES6 Javascript, with the caveat that a final ()is needed to invoke the arguments:
这是一个在 ES6 Javascript 中使用通用可变参数 curry 函数的解决方案，但需要注意的()是，需要使用 final来调用参数：
const curry = (f) =>
(...args) => args.length? curry(f.bind(0, ...args)): f();
const sum = (...values) => values.reduce((total, current) => total + current, 0)
curry(sum)(2)(2)(1)() == 5 // true
Here's another one that doesn't need (), using valueOfas in @rafael's answer. I feel like using valueOfin this way (or perhaps at all) is very confusing to people reading your code, but each to their own.
这是另一个不需要的()，valueOf在@rafael 的回答中使用。我觉得valueOf以这种方式（或者可能根本没有）使用会让阅读您的代码的人感到非常困惑，但每个人都有自己的。
The toStringin that answer is unnecessary. Internally, when javascript performs a type coersion it always calls valueOf()before calling toString().
该toString在这个问题的答案是不必要的。在内部，当 javascript 执行类型转换时，它总是valueOf()在调用toString().
// invokes a function if it is used as a value
const autoInvoke = (f) => Object.assign(f, { valueOf: f } );
const curry = autoInvoke((f) =>
(...args) => args.length? autoInvoke(curry(f.bind(0, ...args))): f());
const sum = (...values) => values.reduce((total, current) => total + current, 0)
curry(sum)(2)(2)(1) + 0 == 5 // true
回答by Jonas Wilms
Another slightly shorter approach:
另一种略短的方法：
const sum = a => b => b? sum(a + b) : a;
Usable as:
可用作：
console.log(
sum(1)(2)(),
sum(3)(4)(5)()
);
回答by Deepak K
New ES6 way and is concise.
新的 ES6 方式并且简洁。
You have to pass empty () at the end when you want to terminate the call and get the final value.
当你想终止调用并获得最终值时，你必须在最后传递 empty() 。
const sum= x => y => !!y ? sum(x + y) : x;
call it like this -
像这样称呼它-
sum(10)(30)(45)();
回答by shekhardtu
Might be an old question but a little extended answer
可能是一个老问题，但答案有点长
function sum() {
var args = [];
args.push(...arguments);
function sumOfAllArguments() {
return args.reduce((prev,items)=>prev + items, 0)
}
function v() {
arguments && args.push(...arguments);
return arguments.length === 0 ? sumOfAllArguments() : v;
}
v.valueOf = v.toString = sumOfAllArguments;
return v;
}
console.log(sum(2)(2)(2)()) // 6
console.log(sum(2)(2)(2).toString()) // 6
console.log(sum(2)(2)(2).valueOf()) // 6
console.log(+sum(2)(2)(2)) //6
console.log(sum(2)(2)(2)) // f 6
console.log(sum(2,2,2)(2,2)(2)) // f 12
console.log(sum(2)(2,2)(2)()) // 8回答by UtkarshPramodGupta
Here's a more generic solution that would work for non-unary params as well:
这是一个更通用的解决方案，它也适用于非一元参数：
const sum = function (...args) {
let total = args.reduce((acc, arg) => acc+arg, 0)
function add (...args2) {
if (args2.length) {
total = args2.reduce((acc, arg) => acc+arg, total)
return add
}
return total
}
return add
}
document.write( sum(1)(2)() , '<br/>') // with unary params
document.write( sum(1,2)() , '<br/>') // with binary params
document.write( sum(1)(2)(3)() , '<br/>') // with unary params
document.write( sum(1)(2,3)() , '<br/>') // with binary params
document.write( sum(1)(2)(3)(4)() , '<br/>') // with unary params
document.write( sum(1)(2,3,4)() , '<br/>') // with ternary params回答by Aliaksandr Sushkevich
Here is another functional way using an iterative process
这是使用迭代过程的另一种功能方式
const sum = (num, acc = 0) => {
if (!num) return acc;
return x => sum(x, acc + num)
}
sum(1)(2)(3)()
and one-line
和单线
const sum = (num, acc = 0) => !num ? acc : x => sum(x, acc + num)
sum(1)(2)(3)()
