Sample implementation of a median calculation function in JavaScript

calculateMedian.js

function calculateMedian( array ) {
  var arraySize = array.length

  if ( arraySize === 1 ) {
    return array[0]
  }
  var isOddLength = isOdd( arraySize ),
    middleIndex = Math.floor( arraySize / 2.0 )

  array.sort( subtract )

  if ( isOddLength ) {
    return array[ middleIndex ]
  }
  return ( array[ middleIndex - 1] + array[ middleIndex ] ) / 2.0
}

function subtract(a, b) {
  return a - b
}

function isOdd( number ) {
  return number % 2 === 1
}