TypeScript sorting an array

Question

I ve been trying to figure out a very strange issue I ran into with typescript  It was treating an inline Boolean expression as whatever the first value s type was instead of the complete expression   So if you try something simple like the following   var numericArray Array lt number gt     2 3 4 1 5 8 11    var sorrtedArray Array lt number gt    numericArray sort  n1 n2   gt  n1  gt  n2     TryIt  You will get an error on your sort method saying the parameters do not match any signature of the call target  because your result is numeric and not Boolean  I guess I m missing something though cause I m pretty sure n1 n2 is a Boolean statement

User · Answer

I wrote this one today while trying to recreate _.sortBy in TypeScript, and thought I would leave it for anyone in need.

// ** Credits for getKeyValue at the bottom **
export const getKeyValue = <T extends {}, U extends keyof T>(key: U) => (obj: T) => obj[key] 

export const sortBy = <T extends {}>(index: string, list: T[]): T[] => {
    return list.sort((a, b): number => {
        const _a = getKeyValue<keyof T, T>(index)(a)
        const _b = getKeyValue<keyof T, T>(index)(b)
        if (_a < _b) return -1
        if (_a > _b) return 1
        return 0
    })
}

Usage:

It expects an array of generic type T, hence the cast for <T extends {}>, as well as typing the parameter and function return type with T[]

const x = [{ label: 'anything' }, { label: 'goes'}]
const sorted = sortBy('label', x)

** getByKey fn found here

User · Answer

Sort Mixed Array  alphabets and numbers    x000D   x000D  function naturalCompare a  b    x000D     var ax       bx       x000D   x000D     a replace    d     D   g  function      1   2    ax push   1    Infinity   2             x000D     b replace    d     D   g  function      1   2    bx push   1    Infinity   2             x000D   x000D     while  ax length  amp  amp  bx length    x000D       var an   ax shift    x000D       var bn   bx shift    x000D       var nn    an 0  - bn 0      an 1  localeCompare bn 1    x000D       if  nn  return nn  x000D       x000D   x000D     return ax length - bx length  x000D    x000D   x000D  let builds      x000D        id  1  name   Build 91     x000D        id  2  name   Build 32      x000D        id  3  name   Build 13      x000D        id  4  name   Build 24     x000D        id  5  name   Build 5     x000D        id  6  name   Build 56    x000D    x000D   x000D  let sortedBuilds   builds sort  n1  n2    gt    x000D    return naturalCompare n1 name  n2 name  x000D     x000D   x000D  console log  Sorted by name property   x000D  console log sortedBuilds  x000D   x000D   x000D

User · Answer

The easiest way seems to be subtracting the second number from the first   var numericArray Array lt number gt     2 3 4 1 5 8 11    var sorrtedArray Array lt number gt    numericArray sort  n1 n2    gt  n1 - n2     https   alligator io js array-sort-numbers

User · Answer

Numbers  When sorting numbers  you can use the compact comparison   var numericArray  number      2  3  4  1  5  8  11    var sortedArray  number     numericArray sort  n1 n2    gt  n1 - n2     i e  - rather than  lt    Other Types  If you are comparing anything else  you ll need to convert the comparison into a number   var stringArray  string       AB    Z    A    AC     var sortedArray  string     stringArray sort  n1 n2    gt        if  n1  gt  n2            return 1             if  n1  lt  n2            return -1             return 0        Objects  For objects  you can sort based on a property  bear in mind the above information about being able to short-hand number types  The below example works irrespective of the type   var objectArray    age  number           age  10     age  1     age  5     var sortedArray    age  number        objectArray sort  n1 n2    gt        if  n1 age  gt  n2 age            return 1             if  n1 age  lt  n2 age            return -1             return 0

User · Answer

let numericArray  number      2  3  4  1  5  8  11    let sortFn    n1   n2    gt  number   return n1 - n2     const sortedArray  number     numericArray sort sortFn     Sort by some field   let arr  key number        key   2    key   3    key   4    key   1    key   5    key   8    key   11     let sortFn2    obj1   obj2    gt   key number    return obj1 key - obj2 key     const sortedArray2  key number      arr sort sortFn2

User · Answer

Great answer Sohnee  Would like to add that if you have an array of objects and you wish to sort by key then its almost the same  this is an example of one that can sort by both date number  or title string        if  sortBy      date             return n1 date - n2 date       else           if  n1 title  gt  n2 title               return 1                    if  n1 title  lt  n2 title                return -1                    return 0          Could also make the values inside as variables n1 field  vs n2 field  if its more dynamic  just keep the diff between strings and numbers

User · Answer

The error is completely correct   As it s trying to tell you   sort   takes a function that returns number  not boolean   You need to return negative if the first item is smaller  positive if it it s larger  or zero if they re equal

[typescript] TypeScript sorting an array

Usage:

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