Question

-1

How can one compare string and numeric values (respecting negative values, with null always last)?

rated 0 times [ 1] [ 2] / answers: 1 / hits: 21361 / 11 Years ago, mon, september 30, 2013, 12:00:00

I'm trying to sort an array of values that can be a mixture of numeric or string values (e.g. [10,20,null,1,bar,-2,-3,null,5,foo]). How can I sort this array such that

null values are always placed last (regardless of sorting order, see jsFiddle)

negative numbers are sorted correctly (i.e. they are less than positive numbers and sort correctly amongst themselves)

? I made a jsFiddle with detailed numeric and string examples (using localeCompare and the numeric option), but will paste the numeric version of my sorting algorithm below as a starting point.

// Sorting order

var order = asc; // Try switching between asc and dsc



// Dummy arrays

var numericArr = [10,20,null,1,-2,-3,null,5];



// Sort arrays

$(.output1).append(numericArr.toString());

numericArr.sort(sortByDataNumeric);

$(.output2).append(numericArr.toString());



// Numeric sorting function

function sortByDataNumeric(a, b, _order) {



    // Replace internal parameters if not used

    if (_order == null) _order = order;



    // If values are null, place them at the end

    var dflt = (_order == asc ? Number.MAX_VALUE : -Number.MAX_VALUE);



    // Numeric values

    var aVal = (a == null ? dflt : a);

    var bVal = (b == null ? dflt : b);

    return _order == asc ? (aVal - bVal) : (bVal - aVal);

}

The problem with my string sorting algorithm (see jsFiddle) is that I can't find a way to always place null values last and negative values aren't correctly sorted within themselves (e.g. -3 should be less than -2)

Edit

To answer the comments, I expect [10,20,null,1,bar,-2,-3,null,5,foo] to sort to [-3,-2,1,5,10,20,bar,foo,null,null]

Answers

Only authorized users can answer the question. Please sign in first, or register a free account.

leslijessalyng

Add To Favorites

Follow

Total Points: 650

Total Questions: 85

Total Answers: 109

Location: Croatia

Member since Mon, Sep 6, 2021

3 Years ago

leslijessalyng questions

1 Vue dist path for CSS and JS not found

Fri, Feb 21, 20, 00:00, 4 Years ago

1 How do I loop through multiple pages in an API?

Tue, Jul 30, 19, 00:00, 5 Years ago

1 ReactJS and autofocus

Fri, Jul 5, 19, 00:00, 5 Years ago

1 How to fix The message port closed before a response was received. after window.location.reload() in javascript

Wed, Apr 3, 19, 00:00, 5 Years ago

1 TypeError: $ .find is not a function

Wed, Mar 13, 19, 00:00, 5 Years ago

View All

answered 11 Years ago anjelicadixied · Accepted Answer

You should first check to see if either value is null and return the opposite value.

On a side note:

For your default _order value, you should check if the parameter is undefined instead of comparing its value to null. If you try to compare something that is undefined directly you will get a reference error:

(undefinedVar == null) // ReferenceError: undefinedVar is not defined

Instead, you should check if the variable is undefined:

(typeof undefinedVar == "undefined") // true

Also, it's probably a better idea to wrap your compare function in a closure instead of relying on a global order variable.

Sometime like:

[].sort(function(a, b){ return sort(a, b, order)})

This way you can sort at a per-instance level.

http://jsfiddle.net/gxFGN/10/

JavaScript

function sort(a, b, asc) {

    var result;



    /* Default ascending order */

    if (typeof asc == "undefined") asc = true;



    if (a === null) return 1;

    if (b === null) return -1;

    if (a === null && b === null) return 0;



    result = a - b;



    if (isNaN(result)) {

        return (asc) ? a.toString().localeCompare(b) : b.toString().localeCompare(a);

    }

    else {

        return (asc) ? result : -result;

    }

}