diff --git a/README.md b/README.md index 1a50c8ec0..d0be53894 100644 --- a/README.md +++ b/README.md @@ -98,6 +98,7 @@ average(1, 2, 3); * [`countOccurrences`](#countoccurrences) * [`deepFlatten`](#deepflatten) * [`difference`](#difference) +* [`differenceBy`](#differenceby) * [`differenceWith`](#differencewith) * [`dropElements`](#dropelements) * [`dropRight`](#dropright) @@ -726,6 +727,32 @@ difference([1, 2, 3], [1, 2, 4]); // [3]
[⬆ Back to top](#table-of-contents) +### differenceBy + +Returns the difference between two arrays, after applying the provided function to each array element of both. + +Create a `Set` by applying `fn` to each element in `b`, then use `Array.filter()` in combination with `fn` on `a` to only keep values not contained in the previously created set. + +```js +const differenceBy = (a, b, fn) => { + const s = new Set(b.map(v => fn(v))); + return a.filter(x => !s.has(fn(x))); +}; +``` + +
+Examples + +```js +differenceBy([2.1, 1.2], [2.3, 3.4], Math.floor); // [1.2] +differenceBy([{ x: 2 }, { x: 1 }], [{ x: 1 }], v => v.x); // [ { x: 2 } ] +``` + +
+ +
[⬆ Back to top](#table-of-contents) + + ### differenceWith Filters out all values from an array for which the comparator function does not return `true`. diff --git a/docs/index.html b/docs/index.html index 0f12043c8..054980965 100644 --- a/docs/index.html +++ b/docs/index.html @@ -50,7 +50,7 @@ scrollToTop(); } }, false); - }

logo 30 seconds of code Curated collection of useful JavaScript snippets that you can understand in 30 seconds or less.

 

Adapter

call

Given a key and a set of arguments, call them when given a context. Primarily useful in composition.

Use a closure to call a stored key with stored arguments.

const call = (key, ...args) => context => context[key](...args);
+      }
logo 30 seconds of code Curated collection of useful JavaScript snippets that you can understand in 30 seconds or less.
 
Adapter
call
Given a key and a set of arguments, call them when given a context. Primarily useful in composition.
Use a closure to call a stored key with stored arguments.
const call = (key, ...args) => context => context[key](...args);
 
Promise.resolve([1, 2, 3])
   .then(call('map', x => 2 * x))
   .then(console.log); //[ 2, 4, 6 ]
@@ -112,6 +112,12 @@ Object.assig
   return a.filter(x => !s.has(x));
 };
 
difference([1, 2, 3], [1, 2, 4]); // [3]
+
differenceBy
Returns the difference between two arrays, after applying the provided function to each array element of both.
Create a Set by applying fn to each element in b, then use Array.filter() in combination with fn on a to only keep values not contained in the previously created set.
const differenceBy = (a, b, fn) => {
+  const s = new Set(b.map(v => fn(v)));
+  return a.filter(x => !s.has(fn(x)));
+};
+
differenceBy([2.1, 1.2], [2.3, 3.4], Math.floor); // [1.2]
+differenceBy([{ x: 2 }, { x: 1 }], [{ x: 1 }], v => v.x); // [ { x: 2 } ]
 
differenceWith
Filters out all values from an array for which the comparator function does not return true.
Use Array.filter() and Array.findIndex() to find the appropriate values.
const differenceWith = (arr, val, comp) => arr.filter(a => val.findIndex(b => comp(a, b)) === -1);
 
differenceWith([1, 1.2, 1.5, 3, 0], [1.9, 3, 0], (a, b) => Math.round(a) === Math.round(b)); // [1, 1.2]
 
dropElements
Removes elements in an array until the passed function returns true. Returns the remaining elements in the array.
Loop through the array, using Array.slice() to drop the first element of the array until the returned value from the function is true. Returns the remaining elements.
const dropElements = (arr, func) => {