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Ilya Kantor 2019-03-23 02:13:30 +03:00
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1-js/06-advanced-functions/11-currying-partials/article.md
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@ -113,14 +113,18 @@ Sometimes people mix up partial function application mentioned above with anothe
[Currying](https://en.wikipedia.org/wiki/Currying) is translating a function from callable as `f(a, b, c)` into callable as `f(a)(b)(c)`. [Currying](https://en.wikipedia.org/wiki/Currying) is translating a function from callable as `f(a, b, c)` into callable as `f(a)(b)(c)`.
Let's make `curry` function that performs currying for binary functions. In other words, it translates `f(a, b)` into `f(a)(b)`: Literally, currying is a transformation of functions: from one way of calling into another. In JavaScript, we usually make a wrapper to keep the original function.
Currying doesn't call a function. It just transforms it. We'll see use cases soon.
Let's make `curry` function that performs currying for two-argument functions. In other words, `curry(f)` for two-argument `f(a, b)` translates it into `f(a)(b)`
```js run ```js run
*!* *!*
function curry(func) { function curry(f) { // curry(f) does the currying transform
return function(a) { return function(a) {
return function(b) { return function(b) {
return func(a, b); return f(a, b);
}; };
}; };
} }
@ -156,7 +160,7 @@ function curry(f) {
## Currying? What for? ## Currying? What for?
Advanced currying allows both to keep the function callable normally and to get partials easily. To understand the benefits we definitely need a worthy real-life example. To understand the benefits we definitely need a worthy real-life example. Advanced currying allows the function to be both callable normally and get partials.
For instance, we have the logging function `log(date, importance, message)` that formats and outputs the information. In real projects such functions also have many other useful features like: sending it over the network or filtering: For instance, we have the logging function `log(date, importance, message)` that formats and outputs the information. In real projects such functions also have many other useful features like: sending it over the network or filtering:
@ -208,7 +212,7 @@ So:
## Advanced curry implementation ## Advanced curry implementation
In case you're interested, here's the "advanced" curry implementation that we could use above. In case you're interested, here's the "advanced" curry implementation that we could use above, it's pretty short:
```js run ```js run
function curry(func) { function curry(func) {
@ -241,7 +245,7 @@ alert( curriedSum(1)(2,3) ); // 6
alert( curriedSum(1)(2)(3) ); // 6 alert( curriedSum(1)(2)(3) ); // 6
``` ```
The new `curry` may look complicated, but it's actually pretty easy to understand. The new `curry` may look complicated, but it's actually easy to understand.
The result of `curry(func)` is the wrapper `curried` that looks like this: The result of `curry(func)` is the wrapper `curried` that looks like this: