Internal implementation principle of sort

sort Basic use of the method ：
arr.sort([compareFunction])
compareFunction A function used to specify a certain order , If you don't write . The element is converted into a string according to unicode Code to sort .

  const months = ['March', 'Jan', 'Feb', 'Dec'];
  months.sort();
  console.log(months);
  const arr1 = [1,23,43,34,5,4,12098];
  arr1.sort();
  console.log(arr1);

You can see , String sorting is no problem . But the numbers are not sorted correctly , Because after the number is converted into a string, the first element of the string unicode Determines the ordering of elements .

So you need to specify compareFunction.
a Value range nums[1] – nums[nums.length-1]
b Value range nums[0] – nums[nums.length-2]

If compareFunction（a, b） Less than 0, that a,b Location switching ;
If compareFunction（a, b） be equal to 0,a and b The relative position of ;
If compareFunction（a, b） Greater than 0,a and b The relative position of .

sort Sorting analysis
If the number of elements to sort is n When , Then there will be the following situations ：
When n<=10 when , Use insert sort ;
When n>10 when , Use a quick sort ;

Theoretically , The time complexity of quick sorting is O（nlogn）, The insertion order is O(n2)
actually , When the amount of data is large , Quick sorting has greater advantages . But when the amount of data is small , Insert sort performance will exceed quick sort .