Function in JS that returns a object with unique values in array and number of times they appear

Question

I'am pretty new to JavaScript and i have this exercise that have been bugging me for a some hours now.

I want to write a Javascript function that expects an array which could contain string and/or numbers (as well as finite levels of nested arrays of strings and/or numbers), and returns a Javascript object which shows the total number of occurences of each unique values.

Something like this

var myArray = [ 1, 2, 1, 'a', [ 'd', 5, 6 ], 'A', 2, 'b', 1, 'd' ];
var myResult = myFunction( myArray );

Then it should return something like this

yourResult = {
    1: 3,
    2: 2,
    'a': 1,
    'd': 2,
    5: 1,
    6: 1,
    'A': 1,
    'b': 1,
}

So far what i have is this. I dont know how to create the object but this is not working at all. It ads all the values in the array

Array.prototype.contains = function(v) {
for(var i = 0; i < this.length; i++) {
    if(this[i] === v) return true;
}
return false;
};

Array.prototype.unique = function() {
var arr = [];
for(var i = 0; i < this.length; i++) {
    if(this[i] instanceof Array) {
        for(var j = 0; i < this[i].length; j++){
        if (!arr.contains(this[i][j])){
            arr.push(this[i][j]);
        }
        } 
    }
    if(!arr.contains(this[i])) {
        arr.push(this[i]);
    }
}
return arr;
}

var myArray = [1,3,4,2,1,[1,2,3,6],2,3,8];
var myResult = duplicates.unique();

console.log(myResult);

You should in fact divide this in two functions: myArray.flatten().count(). A .unique() method would typically only remove duplicates, but not count occurences. — Bergi
– Bergi, Commented May 19, 2015 at 11:34

ItayB · Accepted Answer · 2015-05-19 11:34:55Z

I would seperate it into 2 major problems: 1. Make the array members to be at one level (not nested). 2. Count repeats

The first one I solved with recursion, hope it's meet the requirements. The second is about counting instances..

Hope it's help

Fiddle example

var myArray = [ 1, 2, 1, 'a', [ 'd', 5, 6 ], 'A', 2, 'b', 1, 'd' ];
var myResult = myFunction( myArray );
console.log(myResult);

function myFunction(arr) {
    var r = {};
    for (var i=0 ; i < arr.length ; i++) {
        if( Object.prototype.toString.call( arr[i] ) === '[object Array]' ) {
            var sub = myFunction(arr[i]);
            for (var attrname in sub) { 
                if (r[attrname])
                    r[attrname]++;
                else {
                     r[attrname] = sub[attrname]; 
                    r[attrname] = 1;
                }
            }
        }
        else if (r[arr[i]])
            r[arr[i]]++;
        else
            r[arr[i]] = 1;
    }

    return r;
}

dev_ankit · Accepted Answer · 2015-05-19 11:54:55Z

1

An associative array is what you need to hold the result:

var associative_array={}

then you can use a function like this:

function add_to_as(value){ //Add element to the global associative array
if(associative_array[value]==undefined){
    associative_array[value]=1;
}
else{
    associative_array[value] +=1;//add one
}
}

function myFunction( mydata ){
for(var i = 0; i < mydata.length; i++) {
    if(mydata[i] instanceof Array) { //recurse on sublists if any
        myFunction(mydata[i])
    }
    else{
        add_to_as(mydata[i]);
    }
}
}
//To test the function
var myArray = [ 1, 2, 1, 'a', [ 'd', 5, 6 ], 'A', 2, 'b', 1, 'd' ];
myFunction(myArray);
console.log(associative_array);

edited May 19, 2015 at 11:54

answered May 19, 2015 at 11:45

dev_ankit

5364 silver badges8 bronze badges

Comments

ozil · Accepted Answer · 2015-05-19 12:05:33Z

0

Besides your code
you can put all the elements of your array to a second array containing all the elements of array and sub arrays. Then you can iterate over second array and find the occurrence of each element like this

var arr1 = [1, 2, 1, 'a', ['d', 5, 6], 'A', 2, 'b', 1, 'd'];
var arr = [];
var obj = {};

for (var i = 0; i < arr1.length; i++) {
    if (arr1[i].length == undefined || arr1[i].length == 1) {
        arr.push(arr1[i]);
    }
    else {
        for (var j = 0; j < arr1[i].length; j++) {
            arr.push(arr1[i][j]);
        }
    }
}

for (var i = 0, j = arr.length; i < j; i++) {
    if (obj[arr[i]]) {
        obj[arr[i]]++;
    }
    else {
        obj[arr[i]] = 1;
    }
}

console.log(obj);

DEMO
Updated:In case of nested arrays

var arr2 = [1, 2, 1, 'a', ['d', 5, 6,['d', 5, 6,['d', 5, 6]]], 'A', 2, 'b', 1, 'd'];
var arr = [];
var obj = {};
function singleArray(arr1) {

    for (var i = 0; i < arr1.length; i++) {
        if (arr1[i].length == undefined || arr1[i].length == 1) {
            arr.push(arr1[i]);
        }
        else {
            singleArray(arr1[i]);
        }

    }
}
singleArray(arr2);
for (var i = 0, j = arr.length; i < j; i++) {
    if (obj[arr[i]]) {
        obj[arr[i]]++;
    }
    else {
        obj[arr[i]] = 1;
    }
}
console.log(obj);

DEMO

edited May 19, 2015 at 12:05

answered May 19, 2015 at 11:43

ozil

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1 Comment

ItayB Over a year ago

It's supports only one level of nested array, the question define "finite levels of nested arrays"

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