JavaScript算法题(一) && 数组reduce使用

可参考Array.reduce用法

1. 请编写getMissingElement函数，返回给定数组中缺少的元素（数组里的元素为0~9，只会缺失一个）。

Example:

getMissingElement( [0, 5, 1, 3, 2, 9, 7, 6, 4] ) // returns 8

getMissingElement( [9, 2, 4, 5, 7, 0, 8, 6, 1] ) // returns 3

soluction:

function getMissingElement(superImportantArray){
  return superImportantArray.reduce(function(sum,i){return sum - i;},45)
}

2.Write a function that flattens an Array of Array objects into a flat Array. Your function must only do one level of flattening.

Exmaple:

flatten([123]) // => [1,2,3]

flatten([[1,2,3],["a","b","c"],[1,2,3]])   //=>[1,2,3,"a","b","c",1,2,3]

flatten([[[1,2,3]]])  // => [[1,2,3]]

soluction:

var flatten = function (array){
   return array.reduce(function(a,b){
       return a.concat(b);
   },[])
}