Count Negative Integers in Matrix

negative-number-matrix.js

const
  composeN = (...fs) => y =>
    fs.reduceRight((x, f) => f(x), y)

, flatten = xs =>
    xs.reduce((acc, x) => acc.concat(x))
    
, filter = pred => xs =>
    xs.filter(pred)
    
, negative = x =>
    x < 0
    
, prop = p => o =>
    o[p]

, M = 
  [ [-1, 3,  4, 1]
  , [ 2, 2,  4, 9]
  , [ 4, 5, -7, 9]
  ]  

composeN(
  prop('length'),
  filter(negative),
  flatten
)(M)