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I am stuck at a JavaScript function that should count all unique items in an array

I wanted to create a function, that counts all unique Items in an array, but somehow I do not get any output.
This is my array!
let arr = ["hi", "hello", "hi"];
And this is the code I wrote so far:
function countUnique(arr) {
var counts = {};
for (var i = 0; i < arr.length; i++) {
counts[arr[i]] = 1 + (counts[arr[i]] || 0);
}
countUnique(arr);
}
console.log(countUnique(arr));

Your are counting values correctly, however then you are calling this method recursively countUnique(arr); and it results an error of call stack exceeded.
So just remove recursive call of method countUnique(arr); and return counted value counts:
function countUnique(arr) {
var counts = {};
for (var i = 0; i < arr.length; i++) {
counts[arr[i]] = 1 + (counts[arr[i]] || 0);
}
return counts;
}
let arr = ["hi", "hello", "hi"];
console.log(countUnique(arr));
JavaScript engine limits the maximal recursion depth. We can rely on it being 10000, some engines allow more.

You could take a Set and return the size.
const countUnique = array => new Set(array).size;
console.log(countUnique(["hi", "hello", "hi"]));

let arr = ["hi", "hello", "hi"];
function countUnique(arr) {
var counts = {};
for (var i = 0; i < arr.length; i++) {
if(arr[i] in counts) {
counts[arr[i]]++;
} else {
counts[arr[i]] = 1;
}
}
return Object.keys(counts).length;
}
console.log(countUnique(arr));

Equivalent of set in ES6 to ES5

I have a set over which I am iterating in ES6. I am trying to convert it to its equivalent in ES5. My build is getting failed because of ES6. That's why I am converting it to ES5.
Here's my code in ES6
service.getDevices = function (date) {
var result = [];
var deviceList = devices[date.getTime()];
for (let item of deviceList) { // browser compatibility: support for ECMA6
result.push({"deviceName": item});
}
return result;
}
I am getting error because of 'let'. I tried using for (var item in deviceList), it does not display the charts.
I also tried this:
for(var i = 0; i < deviceList.length(); i++){
result.push({"deviceName" : deviceList[i]});
}
Even this is not working for set. can someone help and tell me how to iterate over a set in ES5 and if that is not possible, is there any equivalent way of doing it?

This is a basic set es5 class that I have used variations on over the years.
function Set(items) {
this._data = {};
this.addItems(items);
}
Set.prototype.addItem = function(value) {
this._data[value] = true;
return this;
}
Set.prototype.removeItem = function(value) {
delete this._data[value];
return this;
}
Set.prototype.addItems = function(values) {
for (var i = 0; i < values.length; i++) {
this.addItem(values[i]);
}
return this;
}
Set.prototype.removeItems = function(values) {
for (var i = 0; i < values.length; i++) {
this.removeItem(values[i]);
}
return this;
}
Set.prototype.contains = function(value) {
return !!this._data[value];
}
Set.prototype.reset = function() {
this._data = {};
return this;
}
Set.prototype.data = function() {
return Object.keys(this._data);
}
Set.prototype.each = function(callback) {
var data = this.data();
for (var i = 0; i < data.length; i++) {
callback(data[i]);
}
}
var set = new Set(['a', 'b', 'c']);
console.log(set.addItems(['a', 'd', 'e']).removeItems(['b', 'e']).data());
console.log(set.contains('a'));
console.log(set.contains('e'));
set.each(console.log)

Why not just iterate through the data and map the result with Array#map.
result = deviceList.map(function (item) {
return { deviceName: item };
});

I think your problem with your second for example is just that length is a property and not a function so you shouldn't add () to the end of it. A working version of this might look like this:
for(var i = 0; i < deviceList.length; i++){
result.push({"deviceName" : deviceList[i]});
}
This assumes (as #grabantot pointed out) that deviceList is an array, however, if it's a Set then you need to use the deviceList.size property.
However, there is a more compatible version of your first for loop which is the forEach() function (which is available on Array and Set), like this:
deviceList.forEach(function (item) {
result.push({"deviceName": item});
});

Getting leaf values from any kind of objects

I am trying to get all leaf value of any kind object as array.
Here is sample object and I want to get [1, 2, 3] from this object.
{
“group1”:[
{
“value1”:”1”,
"value2”:”2”
},
{
“gropu2”:[{
"gropu3”:”3”
}]
}]
}
Here is current implementation.
var t = {
"a":[
{
"a":"1",
"b":"2"
},
{
"d":[{
"e":"3"
}]
}]
}
function getNode( node ){
if(node == null)
return null;
if(typeof node !== 'object'){
return [node];
}
var arr = [];
for( var i = 0; i < node.length ; i ++){
Array.prototype.push.apply(arr, getNode(node[i]));
}
return arr;
}
$(document).ready(function(){
console.log(getNode(t));
});
But it is showing nothing.
I can’t understand where I am doing wrong with my implementation and is there any other easy way to get this done?

The problem is in this line.
for( var i = 0; i < node.length ; i ++){
Here you can not access all element of object using for loop.
You have to convert object to array and then do that.
var array_node = Object.keys(node).map(function(key) { return node[key] });
for( var i = 0; i < array_node.length ; i ++){
Array.prototype.push.apply(arr, getNode(array_node[i]));
}
FIDDLE

Dictionary inside array in Javascript

I have certain data sets. Example, A,B and C. There are sets of these values. For example:-
[A:asd, B:ajs, C:aknd],
[A:sdf, B:gss, C:fdss],
[A:ijq, B:cba, C:jqwd]
etc.
Now i want to make a dictionary containing these values as separate dictionaries. For example:-
{
{
A:asd,
B:ajs,
C:aknd
},
{
A:sdf,
B:gss,
C:fdss
},
{
A:ijq,
B:cba,
C:jqwd
}
}
Can someone help me out with this.
I tried doing this but it's not making a dictionary.
for( var i=0; i< n; i++) {
data += {
"A":value1,
"B":value2,
"C":value3
}
}
Any inputs?

This does not make sense in Javascript:
{
{
A:asd,
B:ajs,
C:aknd
},
{
A:sdf,
B:gss,
C:fdss
},
{
A:ijq,
B:cba,
C:jqwd
}
}
If you intend to have an object (dictionary) with integer keys, you could do it like so:
var data = {};
for( var i=0; i< n; i++) {
data[i] = {
"A":value1,
"B":value2,
"C":value3
}
}
Depending a bit on what you're trying to do, an array would likely be a better choice:
var data = [];
for( var i=0; i< n; i++) {
data.push({
"A":value1,
"B":value2,
"C":value3
});
}

Create array based on object properties

I'd like to use an object to configure some settings for an app. My idea is to start with this:
var obj = {
property_one: 3;
property_two: 2;
property_three: 1;
}
And I would like to end up with this:
var array = [
'property_one','property_one','property_one',
'property_two','property_two',
'property_three'
]
My current solution is to do this for each property:
function theConstructor(){
for(i=1; i <= obj.property_one; i++){
this.array.push('property_one');
};
for(i=1; i <= obj.property_two; i++){
this.array.push('property_two');
};
for(i=1; i <= obj.property_two; i++){
this.array.push('property_two');
};
}
But this gets tedious, because I might have many properties, and these might change as the app evolves.
I know I can loop through object's properties like this:
for (var key in obj) {
if (obj.hasOwnProperty(key)) {
array.push(key);
}
}
But this will push the value to the array, not the key (as a string). Any ideas about how I can do this more efficiently?

Try this
function theConstructor(){
for (var key in obj) {
if (obj.hasOwnProperty(key)) {
for(var i=1; i <= obj[key]; i++){
this.array.push(key);
};
}
}
}

Using Array.prototype.reduce():
var obj = {
property_one: 3,
property_two: 2,
property_three: 1
};
var resultArray = Object.keys(obj).reduce(function(result, curItem) {
for (var index = 0; index < obj[curItem]; index++) {
result.push(curItem);
}
return result;
}, []);
document.write(JSON.stringify(resultArray));