Added all math By snippets

snippets/averageBy.md

@@ -0,0 +1,13 @@
+### averageBy
+
+Returns the average of an array, after mapping each element to a value using the provided function.
+
+Use `Array.map()` to map each element to the value returned by `fn`, `Array.reduce()` to add each value to an accumulator, initialized with a value of `0`, divide by the `length` of the array.
+
+```js
+const averageBy = (arr, fn) => arr.map(fn).reduce((acc, val) => acc + val, 0)/arr.length;
+```
+
+```js
+averageBy([{ 'n': 4 }, { 'n': 2 }, { 'n': 8 }, { 'n': 6 }], o => o.n); // 5
+```

snippets/maxBy.md

@@ -0,0 +1,13 @@
+### maxBy
+
+Returns the maximum value of an array, after mapping each element to a value using the provided function.
+
+Use `Array.map()` to map each element to the value returned by `fn`, `Math.max()` to get the maximum value.
+
+```js
+const maxBy = (arr, fn) => Math.max(...arr.map(fn));
+```
+
+```js
+maxBy([{ 'n': 4 }, { 'n': 2 }, { 'n': 8 }, { 'n': 6 }], o => o.n);  // 8
+```

snippets/minBy.md

@@ -0,0 +1,13 @@
+### minBy
+
+Returns the minimum value of an array, after mapping each element to a value using the provided function.
+
+Use `Array.map()` to map each element to the value returned by `fn`, `Math.min()` to get the maximum value.
+
+```js
+const minBy = (arr, fn) => Math.min(...arr.map(fn));
+```
+
+```js
+minBy([{ 'n': 4 }, { 'n': 2 }, { 'n': 8 }, { 'n': 6 }], o => o.n);  // 8
+```

snippets/sumBy.md

@@ -0,0 +1,13 @@
+### sumBy
+
+Returns the sum of an array, after mapping each element to a value using the provided function.
+
+Use `Array.map()` to map each element to the value returned by `fn`, `Array.reduce()` to add each value to an accumulator, initialized with a value of `0`.
+
+```js
+const sumBy = (arr, fn) => arr.map(fn).reduce((acc, val) => acc + val, 0);
+```
+
+```js
+sumBy([{ 'n': 4 }, { 'n': 2 }, { 'n': 8 }, { 'n': 6 }], o => o.n); // 20
+```

tag_database

@@ -1,6 +1,7 @@
 anagrams:string,recursion
 arrayToHtmlList:browser,array
 average:math,array
+averageBy:math,array,function
 bottomVisible:browser
 byteSize:string
 call:adapter,function
@@ -102,9 +103,11 @@ lowercaseKeys:object
 luhnCheck:math,utility
 mapObject:array,object
 mask:string,utility,regexp
+maxBy:math,array,function
 maxN:array,math
 median:math,array
 memoize:function
+minBy:math,array,function
 minN:array,amth
 negate:function
 nthElement:array
@@ -158,6 +161,7 @@ splitLines:string
 spreadOver:adapter
 standardDeviation:math,array
 sum:math,array
+sumBy:math,array,function
 sumPower:math
 symmetricDifference:array,math
 tail:array