diff --git a/README.md b/README.md index 7308593a0..557d44232 100644 --- a/README.md +++ b/README.md @@ -42,6 +42,7 @@ * [Object from key value pairs](#object-from-key-value-pairs) * [Pipe](#pipe) * [Powerset](#powerset) +* [Promisify](#promisify) * [Random integer in range](#random-integer-in-range) * [Random number in range](#random-number-in-range) * [Randomize order of array](#randomize-order-of-array) @@ -416,6 +417,24 @@ const powerset = arr => // powerset([1,2]) -> [[], [1], [2], [2,1]] ``` +### Promisify + +Creates a promise version of the given callback-style function. In Node 8+, you +can use [`util.promisify`](https://nodejs.org/api/util.html#util_util_promisify_original) + +```js +const promisify = func => + (...args) => + new Promise((resolve, reject) => + func(...args, (err, result) => + err + ? reject(err) + : resolve(result)) + ) +// const stat = promisify(fs.stat) +// When called, stat returns a promise +``` + ### Random integer in range Use `Math.random()` to generate a random number and map it to the desired range, using `Math.floor()` to make it an integer. diff --git a/snippets/promisify.md b/snippets/promisify.md new file mode 100644 index 000000000..b2007a5ab --- /dev/null +++ b/snippets/promisify.md @@ -0,0 +1,17 @@ +### Promisify + +Creates a promise version of the given callback-style function. In Node 8+, you +can use [`util.promisify`](https://nodejs.org/api/util.html#util_util_promisify_original) + +```js +const promisify = func => + (...args) => + new Promise((resolve, reject) => + func(...args, (err, result) => + err + ? reject(err) + : resolve(result)) + ) +// const stat = promisify(fs.stat) +// When called, stat returns a promise +```