30-seconds-of-code/snippets/sqaure_it.md

Square The Data

Pass an array of integers you want to sqaure it Here using .reduce() the new object is accumulator and one by one values from array are passed and go through function.

const arr = [1,2,3,4,5,6,7];
arr.reduce(function(a,b){
a[b] = b * b;
return a;
},{}) // {1: 1, 2: 4, 3: 9, 4: 16, 5: 25, 6: 36, 7: 49}
// 
callback	accumulator	currentValue	currentIndex	array	           return value
first call	1	              1		        0        [0, 1, 2, 3, 4]	  1
second call	2	              2		        1        [0, 1, 2, 3, 4]	  4
third call	3	              3		        2        [0, 1, 2, 3, 4]	  9
...