5. 함수형 프로그래밍 - reduce

function reduce( $list, $fn, $memo )

{

let memo = $memo;

each( $list, ( $item ) => memo = $fn( memo, $item ));

return memo;

}

function each( $list, $fn ){

for( let item of $list ){

$fn( item );

}

}

const add = ( a, b ) => a + b;

const minus = ( a, b ) => a - b;

console.log( reduce([ 1, 2, 3 ], add, 0 ));

console.log( reduce([ 1, 2, 3 ], minus, 6 ));