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CODE EXAMPLE FOR JAVASCRIPT

javascript reduce

let arr = [1,2,3]

/*
reduce takes in a callback function, which takes in an accumulator
and a currentValue.

accumulator = return value of the previous iteration
currentValue = current value in the array

*/

// So for example, this would return the total sum:

const totalSum = arr.reduce(function(accumulator, currentVal) {
	return accumulator + currentVal
}, 0);

> totalSum == 0 + 1 + 2 + 3 == 6

/* 
The '0' after the callback is the starting value of whatever is being 
accumulated, if omitted it will default to whatever the first value in 
the array is, i.e: 

> totalSum == 1 + 2 + 3 == 6

if the starting value was set to -1 for ex, the totalSum would be:
> totalSum == -1 + 1 + 2 + 3 == 5
*/


// arr.reduceRight does the same thing, just from right to left
Source by jsbin.com #
 
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7+5 =