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Pablo Ezequiel Inchausti
Asked: 2020-03-24 21:54:08 +0800 CST 2020-03-24 21:54:08 +0800 CST

Error when sorting an array with negative numbers with the JavaScript sort function

  • 772

I am trying to sort the following array that contains negative numbers and the function sort()does not sort it correctly (precisely the negative numbers)

let aa = [1,-2,3,-4,5].sort();
console.log(aa);

It returns me:

[-2, -4, 1, 3, 5]

But I expected the order from smallest to largest

[-4, -2, 1, 3, 5]

What am I doing or misinterpreting?

javascript

1 Answers

  1. Best Answer

    Array#sort( )sorts in UTF-8 order , after converting elements to strings.

    According to the above, first take the -, and then the number itself. And, in UTF-8 encoding, the value of 2is less than the value of 4. And that of the sign -, less than that of any digit or letter.

    If you want to sort the content as numbers, you have to pass it a function as an argument, of the type

    SortFunction( a, b )

    This function will receive 2 of the values ​​of the array, and has to return

    • < 0Yesa < b
    • == 0Yesa == b
    • > 0Yesa > b

    Example:

    [1,-2,3,-4,5].sort( function( a, b ) { return a < b ? -1 : 1; } );

    Departure:

    [-4, -2, 1, 3, 5]

     console.log([1,-2,3,-4,5].sort( function( a, b ) { return a < b ? -1 : 1; } ));

    Note: in the example, it is certain that 2 elements will never be the same, so we save ourselves the check (we never return 0).

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