Sorting objects by property values

Question

How to implement the following scenario using Javascript only:

• Create a car object with properties (top speed, brand, etc.)
• Sort a list of cars ordered by those properties

Answer 1

Example.

This runs on cscript.exe, on windows.

// define the Car class
(function() {
    // makeClass - By John Resig (MIT Licensed)
    // Allows either new User() or User() to be employed for construction.
    function makeClass(){
        return function(args){
            if ( this instanceof arguments.callee ) {
                if ( typeof this.init == "function" )
                    this.init.apply( this, (args && args.callee) ? args : arguments );
            } else
                return new arguments.callee( arguments );
        };
    }

    Car = makeClass();

    Car.prototype.init = function(make, model, price, topSpeed, weight) {
        this.make = make;
        this.model = model;
        this.price = price;
        this.weight = weight;
        this.topSpeed = topSpeed;
    };
})();


// create a list of cars
var autos = [
    new Car("Chevy", "Corvair", 1800, 88, 2900),
    new Car("Buick", "LeSabre", 31000, 138, 3700),
    new Car("Toyota", "Prius", 24000, 103, 3200),
    new Car("Porsche", "911", 92000, 155, 3100),
    new Car("Mercedes", "E500", 67000, 145, 3800),
    new Car("VW", "Passat", 31000, 135, 3700)
];

// a list of sorting functions
var sorters = {
    byWeight : function(a,b) {
        return (a.weight - b.weight);
    },
    bySpeed : function(a,b) {
        return (a.topSpeed - b.topSpeed);
    },
    byPrice : function(a,b) {
        return (a.price - b.price);
    },
    byModelName : function(a,b) {
        return ((a.model < b.model) ? -1 : ((a.model > b.model) ? 1 : 0));
    },
    byMake : function(a,b) {
        return ((a.make < b.make) ? -1 : ((a.make > b.make) ? 1 : 0));
    }
};

function say(s) {WScript.Echo(s);}

function show(title)
{
    say ("sorted by: "+title);
    for (var i=0; i < autos.length; i++) {
        say("  " + autos[i].model);
    }
    say(" ");
}

autos.sort(sorters.byWeight);
show("Weight");

autos.sort(sorters.byModelName);
show("Name");

autos.sort(sorters.byPrice);
show("Price");

You can also make a general sorter.

var byProperty = function(prop) {
    return function(a,b) {
        if (typeof a[prop] == "number") {
            return (a[prop] - b[prop]);
        } else {
            return ((a[prop] < b[prop]) ? -1 : ((a[prop] > b[prop]) ? 1 : 0));
        }
    };
};

autos.sort(byProperty("topSpeed"));
show("Top Speed");

Answer 2

javascript has the sort function which can take another function as parameter - that second function is used to compare two elements.

Example:

cars = [

    {
        name: "Honda",
        speed: 80
    },

    {
        name: "BMW",
        speed: 180
    },

    {
        name: "Trabi",
        speed: 40
    },

    {
        name: "Ferrari",
        speed: 200
    }
]


cars.sort(function(a, b) { 
    return a.speed - b.speed;
})

for(var i in cars)
    document.writeln(cars[i].name) // Trabi Honda BMW Ferrari 

ok, from your comment i see that you're using the word 'sort' in a wrong sense. In programming "sort" means "put things in a certain order", not "arrange things in groups". The latter is much simpler - this is just how you "sort" things in the real world

• make two empty arrays ("boxes")
• for each object in your list, check if it matches the criteria
• if yes, put it in the first "box"
• if no, put it in the second "box"

Answer 3

With ES6 arrow functions it will be like this:

//Let's say we have these cars
let cars = [ { brand: 'Porsche', top_speed: 260 },
  { brand: 'Benz', top_speed: 110 },
  { brand: 'Fiat', top_speed: 90 },
  { brand: 'Aston Martin', top_speed: 70 } ]

Array.prototype.sort() can accept a comparator function (here I used arrow notation, but ordinary functions work the same):

let sortedByBrand = [...cars].sort((first, second) => first.brand > second.brand)

// [ { brand: 'Aston Martin', top_speed: 70 },
//   { brand: 'Benz', top_speed: 110 },
//   { brand: 'Fiat', top_speed: 90 },
//   { brand: 'Porsche', top_speed: 260 } ]

The above approach copies the contents of cars array into a new one and sorts it alphabetically based on brand names. Similarly, you can pass a different function:

let sortedBySpeed =[...cars].sort((first, second) => first.top_speed > second.top_speed)

//[ { brand: 'Aston Martin', top_speed: 70 },
//  { brand: 'Fiat', top_speed: 90 },
//  { brand: 'Benz', top_speed: 110 },
//  { brand: 'Porsche', top_speed: 260 } ]

If you don't mind mutating the orginal array cars.sort(comparatorFunction) will do the trick.

Answer 4

A version of Cheeso solution with reverse sorting, I also removed the ternary expressions for lack of clarity (but this is personal taste).

function(prop, reverse) {
  return function(a, b) {
    if (typeof a[prop] === 'number') {
      return (a[prop] - b[prop]);
    }

    if (a[prop] < b[prop]) {
      return reverse ? 1 : -1;
    }

    if (a[prop] > b[prop]) {
      return reverse ? -1 : 1;
    }

    return 0;
  };
};

Answer 5

I have wrote this simple function for myself:

function sortObj(list, key) {
    function compare(a, b) {
        a = a[key];
        b = b[key];
        var type = (typeof(a) === 'string' ||
                    typeof(b) === 'string') ? 'string' : 'number';
        var result;
        if (type === 'string') result = a.localeCompare(b);
        else result = a - b;
        return result;
    }
    return list.sort(compare);
}

for example you have list of cars:

var cars= [{brand: 'audi', speed: 240}, {brand: 'fiat', speed: 190}];
var carsSortedByBrand = sortObj(cars, 'brand');
var carsSortedBySpeed = sortObj(cars, 'speed');

Answer 6

Here's a short example, that creates and array of objects, and sorts numerically or alphabetically:

// Create Objects Array

var arrayCarObjects = [
{brand: "Honda",        topSpeed: 45},
{brand: "Ford",         topSpeed: 6},
{brand: "Toyota",       topSpeed: 240},
{brand: "Chevrolet",    topSpeed: 120},
{brand: "Ferrari",      topSpeed: 1000}
];

// Sort Objects Numerically

arrayCarObjects.sort((a, b) => (a.topSpeed - b.topSpeed));

// Sort Objects Alphabetically

arrayCarObjects.sort((a, b) => (a.brand > b.brand) ? 1 : -1);