How can you sort an array without mutating the original array

Question

Let s suppose I wanted a sort function that returns a sorted copy of the inputted array  I naively tried this  function sort arr      return arr sort        and I tested it with this  which shows that my sort method is mutating the array   var a    2 3 7 5 3 7 1 3 4   sort a   alert a      alerts  1 2 3 3 3 4 5 7 7    I also tried this approach  function sort arr      return Array prototype sort arr       but it doesn t work at all   Is there a straightforward way around this  prefereably a way that doesn t require hand-rolling my own sorting algorithm or copying every element of the array into a new one

User · Answer

You can use slice with no arguments to copy an array   var foo      bar  foo    3 1 2   bar   foo slice   sort

User · Answer

Try the following  function sortCopy arr       return arr slice 0  sort        The slice 0  expression creates a copy of the array starting at element 0

User · Answer

Anyone who wants to do a deep copy  e g  if your array contains objects  can use   let arrCopy   JSON parse JSON stringify arr     Then you can sort arrCopy without changing arr   arrCopy sort  obj1  obj2    gt  obj1 id  gt  obj2 id    Please note  this can be slow for very large arrays

User · Answer

You can also do this   d    20  30  10  e   Array from d  e sort     This way d will not get mutated    function sorted arr      temp   Array from arr    return temp sort        Use it like this x    20  10  100  console log sorted x

User · Answer

Just copy the array  There are many ways to do that   function sort arr      return arr concat   sort          Or  return Array prototype slice call arr  sort       For array-like objects

User · Answer

You need to copy the array before you sort it  One way with es6  const sorted       arr  sort     the spread-syntax as array literal  copied from mdn   var arr    1  2  3   var arr2       arr      like arr slice    https   developer mozilla org en-US docs Web JavaScript Reference Operators Spread operator

[javascript] How can you sort an array without mutating the original array?

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