Develop Reference

NaN after adding particular key element in an Array object

I have an Array object with 3000 objects. Among these 3000 few of them have grade and few object doesn't. Now I want to sum the grades. I'm getting NaN. Could you please guide me what am I doing wrong. Below is the sample code:
const arr=[
{
"name":"Harvey",
"grade":3
},
{
"name":"Pamela",
},
{
"name":"Scott",
"grade":4
},
{
"name":"Joshua",
"grade":5
},{
"name":"Rachel",
},{
"name":"Harvey",
"grade":3
},
]
let classTotal = arr.reduce(function (previousValue, currentValue) {
return {
grade: (previousValue.grade + currentValue.grade)
}
})
console.log(classTotal) //NaN
Also tried the following:
let classTotal=arr.reduce((accum, item) => accum + item.total, 0)
console.log(classTotal) // Same NaN

If either of the .grade values is itself not a number (such as undefined) then it will break the ongoing calculations. One approach could be to default it to 0 when no value is present. So instead of currentValue.grade you might use (currentValue.grade ?? 0). For example:
const arr=[
{
"name":"Harvey",
"grade":3
},
{
"name":"Pamela",
},
{
"name":"Scott",
"grade":4
},
{
"name":"Joshua",
"grade":5
},
{
"name":"Rachel",
},
{
"name":"Harvey",
"grade":3
},
];
let classTotal = arr.reduce(function (previousValue, currentValue) {
return {
grade: (previousValue.grade + (currentValue.grade ?? 0))
};
});
console.log(classTotal);

NaN is "Not a valid Number" you have some entries missing grade you should run filter to filter them out before your reduce
const arr = [{
"name": "Harvey",
"grade": 3
},
{
"name": "Pamela",
},
{
"name": "Scott",
"grade": 4
},
{
"name": "Joshua",
"grade": 5
}, {
"name": "Rachel",
}, {
"name": "Harvey",
"grade": 3
},
]
let classTotal = arr.filter(function(element) {
return element.grade
}).reduce(function(previousValue, currentValue) {
return {
grade: (previousValue.grade + currentValue.grade)
}
})
console.log(classTotal)
Or, you can add a 0 for example for the elements who does not have a grade:
const arr = [{
"name": "Harvey",
"grade": 3
},
{
"name": "Pamela",
},
{
"name": "Scott",
"grade": 4
},
{
"name": "Joshua",
"grade": 5
}, {
"name": "Rachel",
}, {
"name": "Harvey",
"grade": 3
},
]
let classTotal = arr.reduce(function(previousValue, currentValue) {
return {
grade: (previousValue.grade + (currentValue.grade || 0))
}
})
console.log(classTotal)

Forming JSON with Key and Value if Key Exists

I have a JSON Structure something like:
[
{
"name":"angelinas"
},
{
"name":"besuto"
},
{
"name":"catch",
"cuisine":"Japanese"
},
{
"name":"center cut"
},
{
"name":"fedora"
},
{
"name":"Habanero",
"cuisine":"Mexican"
},
{
"name":"Indies"
},
{
"name":"new"
},
{
"name":"RazINN"
},
{
"name":"restaurantTestVenue779"
},
{
"name":"restaurantTestVenue9703"
},
{
"name":"Salsa ",
"cuisine":"Mexican"
},
{
"name":"Sushi Place",
"cuisine":"Japanese"
},
{
"name":"The Ashoka"
},
{
"name":"The Poboys"
},
{
"name":"the shogun"
},
{
"name":"vinyard view"
}
]
Using the JSON above i want to identify whether a cuisine is assosiated to restaurant. If yes, I want to build a JSON Structure something like:
[
{
"Mexican":{
"venueNames":[
"Habanero",
"Salsa"
]
}
},
{
"Japanese":{
"venueNames":[
"Sushi Place",
"catch"
]
}
}
]
Have tried to build the JSON using a for loop and .hasProperty but not much of a success.

Here is what you can do!
First iterate through the data and use the method "hasOwnProperty" to check if the cuisine exists and if it does then check if your cuisines object has that cuisine and if does then add it to it.
const data = [{
"name": "angelinas"
},
{
"name": "besuto"
},
{
"name": "catch",
"cuisine": "Japanese"
},
{
"name": "center cut"
},
{
"name": "fedora"
},
{
"name": "Habanero",
"cuisine": "Mexican"
},
{
"name": "Indies"
},
{
"name": "new"
},
{
"name": "RazINN"
},
{
"name": "restaurantTestVenue779"
},
{
"name": "restaurantTestVenue9703"
},
{
"name": "Salsa ",
"cuisine": "Mexican"
},
{
"name": "Sushi Place",
"cuisine": "Japanese"
},
{
"name": "The Ashoka"
},
{
"name": "The Poboys"
},
{
"name": "the shogun"
},
{
"name": "vinyard view"
}
]
let cuisines = {};
for (const resturant of data) {
if (resturant.hasOwnProperty('cuisine')) {
if (cuisines.hasOwnProperty(resturant.cuisine)) {
cuisines[resturant.cuisine].venueNames.push(resturant.name);
} else {
cuisines[resturant.cuisine] = {
venueNames: [resturant.name]
};
}
}
}

You can use in one loop below.
data.forEach(function(item) {
// if item has cuisine and cuisine not exist in new array
if(item["cuisine"] != null && typeof newArr.find(v => v[item.cuisine] != null) == 'undefined') {
// create new object with structure
let obj = {};
obj[item.cuisine] = {
"venueNames":[item.name]
};
newArr.push(obj);
}
else {
// else find existing cuisine and add new venue
let obj = newArr.find(v => v.hasOwnProperty(item.cuisine));
if(typeof obj != 'undefined') {
obj[item.cuisine].venueNames.push(item.name);
}
}
});
JSFIDDLE

It's a simple reduction of the array. If the restaurant has a defined cuisine, check if the result already has this cuisine defined. If not, create an object for it where you can push the restaurant name to.
const restaurants = [
{
"name":"angelinas"
},
{
"name":"besuto"
},
{
"name":"catch",
"cuisine":"Japanese"
},
{
"name":"center cut"
},
{
"name":"fedora"
},
{
"name":"Habanero",
"cuisine":"Mexican"
},
{
"name":"Indies"
},
{
"name":"new"
},
{
"name":"RazINN"
},
{
"name":"restaurantTestVenue779"
},
{
"name":"restaurantTestVenue9703"
},
{
"name":"Salsa ",
"cuisine":"Mexican"
},
{
"name":"Sushi Place",
"cuisine":"Japanese"
},
{
"name":"The Ashoka"
},
{
"name":"The Poboys"
},
{
"name":"the shogun"
},
{
"name":"vinyard view"
}
];
const cuisines = restaurants.reduce((result, restaurant ) => {
if ( restaurant.hasOwnProperty( 'cuisine' )) {
const { cuisine } = restaurant;
if ( !result.hasOwnProperty( cuisine )) {
result[ cuisine ] = {
venueNames: []
};
}
result[ cuisine ].venueNames.push( restaurant.name );
}
return result;
}, {});
console.log( cuisines );
In my personal opinion, I would use a slightly different structure though. If we represent collections with objects that are always the same, we can simplify most transformations. This is less efficient that doing everything in one loop, but the code used to create the transformation is almost readable english:
const restaurants = [
{ "name": "angelinas", "cuisine": null },
{ "name": "besuto", "cuisine": null },
{ "name": "catch", "cuisine": "japanese" },
{ "name": "center cut", "cuisine": null },
{ "name": "fedora", "cuisine": null },
{ "name": "habanero", "cuisine": "mexican" },
{ "name": "Indies", "cuisine": null },
{ "name": "new", "cuisine": null },
{ "name": "RazINN", "cuisine": null },
{ "name": "restaurantTestVenue779", "cuisine": null },
{ "name": "restaurantTestVenue9703", "cuisine": null },
{ "name": "Salsa ", "cuisine": "mexican" },
{ "name": "Sushi Place", "cuisine": "japanese" },
{ "name": "The Ashoka", "cuisine": null },
{ "name": "The Poboys", "cuisine": null },
{ "name": "the shogun", "cuisine": null },
{ "name": "vinyard view", "cuisine": null }
];
const create_cuisine = name => ({ name, "venues": [] });
const unique = () => {
const seen = {};
return item => {
const json = JSON.stringify( item );
return seen.hasOwnProperty( json )
? false
: ( seen[ json ] = true );
};
};
// Filter away all the restaurants without a cuisine value.
const restaurants_with_cuisine = restaurants.filter( restaurant => restaurant.cuisine );
const cuisines = restaurants_with_cuisine
// Extract the cuisine anmes from the restaurants.
.map( restaurant => restaurant.cuisine )
// Filter aways all the duplicates.
.filter( unique() )
// Create a new cuisine object.
.map( cuisine_name => create_cuisine( cuisine_name ));
// Finally add all the restaurant names to the right cuisine.
restaurants_with_cuisine.forEach( restaurant => cuisines.find( cuisine => cuisine.name === restaurant.cuisine ).venues.push( restaurant.name ));
console.log( cuisines );

Using a few es6 features, we can generate this list with Set, map and filter.
We will first map a list of cuisines, and remove invalid ones such as undefined. With that we will use a Set to create a unique list of cuisines.
Next we will take that list and map it again to return the final object, by filtering the original object where the cuisine matches the current iteration. Finally we map the filtered results to return just the name to the venueNames object.
Our result will look like this:
function getItems(places) {
// Get a unique list of cuisines
return [...new Set(places.map(p => p.cuisine).filter(c => c))]
// Build the result
.map(c => {
return {
[c]: {
// Get a list of cuisines that match the current cuisine
venueNames: places.filter(p => p.cuisine == c).map(c => c.name)
}
}
})
}
const places = [
{"name": "angelinas"},
{"name": "besuto"},
{"name": "catch","cuisine": "Japanese"},
{"name": "center cut"},
{"name": "fedora"},
{"name": "Habanero","cuisine": "Mexican"},
{"name": "Indies"},
{"name": "new"},
{"name": "RazINN"},
{"name": "restaurantTestVenue779"},
{"name": "restaurantTestVenue9703"},
{"name": "Salsa ","cuisine": "Mexican"},
{"name": "Sushi Place","cuisine": "Japanese"},
{"name": "The Ashoka"},
{"name": "The Poboys"},
{"name": "the shogun"},
{"name": "vinyard view"}
]
console.log(getItems(places))

Parse array of objects recursively and filter object based on id

i have this array of objects : getCategory (variable)
[
{
"id": "20584",
"name": "Produits de coiffure",
"subCategory": [
{
"id": "20590",
"name": "Coloration cheveux",
"subCategory": [
{
"id": "20591",
"name": "Avec ammoniaque"
},
{
"id": "20595",
"name": "Sans ammoniaque"
},
{
"id": "20596",
"name": "Soin cheveux colorés"
},
{
"id": "20597",
"name": "Protection"
},
{
"id": "20598",
"name": "Nuancier de couleurs"
}
]
},
{
"id": "20593",
"name": "Soins cheveux",
"subCategory": [
{
"id": "20594",
"name": "Shampooing"
},
{
"id": "20599",
"name": "Après-shampooing"
},
{
"id": "20600",
"name": "Masques"
},
and i tried everything i could search in stackoverflow ..
lets say on this array i want to get recursively and object with the specified id .. like 20596 and it should return
{
"id": "20596",
"name": "Soin cheveux colorés"
}
The logic way i am doing is like this :
var getSubcategory = getCategory.filter(function f(obj){
if ('subCategory' in obj) {
return obj.id == '20596' || obj.subCategory.filter(f);
}
else {
return obj.id == '20596';
}
});
dont know what else to do .
Thanks
PS : I dont use it in browser so i cannot use any library . Just serverside with no other library . find dont work so i can only use filter

You need to return the found object.
function find(array, id) {
var result;
array.some(function (object) {
if (object.id === id) {
return result = object;
}
if (object.subCategory) {
return result = find(object.subCategory, id);
}
});
return result;
}
var data = [{ id: "20584", name: "Produits de coiffure", subCategory: [{ id: "20590", name: "Coloration cheveux", subCategory: [{ id: "20591", name: "Avec ammoniaque" }, { id: "20595", name: "Sans ammoniaque" }, { id: "20596", name: "Soin cheveux colorés" }, { id: "20597", name: "Protection" }, { id: "20598", name: "Nuancier de couleurs" }] }, { id: "20593", name: "Soins cheveux", subCategory: [{ id: "20594", name: "Shampooing" }, { id: "20599", name: "Après-shampooing" }, { id: "20600", name: "Masques" }] }] }];
console.log(find(data, '20596'));
console.log(find(data, ''));

How to return object based on value in nested array? (Javascript)

I am trying to return all objects that have a specific 'id' in the nested array. In the sample data, I'd like to return all person objects with hobbies id of 2 (hiking).
The other question addresses the problem of finding all values in an array based on an object value.
This question differs from the previous because I need to return all objects based on a value inside of a nested array.
[
{
"id":111222,
"name":"Faye",
"age":27,
"hobbies":[
{
"id":2,
"name":"hiking"
},
{
"id":3,
"name":"eating"
}
]
},
{
"id":223456789001,
"name":"Bobby",
"age":35,
"hobbies":[
{
"id":2,
"name":"hiking"
},
{
"id":4,
"name":"online gaming"
}
]
}
]

function hasHobby(person, hobbyId) {
return person.hobbies.some(function(hobby) {
return hobby.id === hobbyId;
});
}
function filterByHobby(people, hobbyId) {
return people.filter(function(person) {
return hasHobby(person, hobbyId);
});
}
If you wanna use the new cool ES6 syntax:
function filterByHobby(people, hobbyId) {
return people.filter(
person => person.hobbies.some(
hobby => hobby.id === hobbyId
)
);
}

var arr = [
{
"id":111222,
"name":"Faye",
"age":27,
"hobbies":[
{
"id":2,
"name":"hiking"
},
{
"id":3,
"name":"eating"
}
]
},
{
"id":223456789001,
"name":"Bobby",
"age":35,
"hobbies":[
{
"id":2,
"name":"hiking"
},
{
"id":4,
"name":"online gaming"
}
]
}
];
arr.filter(function(obj) {
var hobbies = obj.hobbies;
var x = hobbies.filter(function(hob) {
if (hob.id == "2") return true;
});
if (x.length > 0) return true;
});

Try this, I think its solve your proble:
var arr = [{
"id": 111222,
"name": "Faye",
"age": 27,
"hobbies": [{
"id": 2,
"name": "hiking"
}, {
"id": 3,
"name": "eating"
}]
}, {
"id": 223456789001,
"name": "Bobby",
"age": 35,
"hobbies": [{
"id": 2,
"name": "hiking"
}, {
"id": 4,
"name": "online gaming"
}]
}];
var x = arr.filter(function(el) {
var rnel = el.hobbies.filter(function(nel) {
return nel.id == 2;
});
return rnel.length > 0 ? true :false;
});
alert(x.length);

Reading a JSON output in JavaScript with a lot of objects

This is my JSON output:
[
{
"Business": [
{
"id": "5739"
},
{
"userid": ""
},
{
"name": "Ben Electric"
},
{
"description": ""
},
{
"address": ""
},
{
"email": "*****#gmail.com"
},
{
"phone2": "050*****88"
},
{
"phone3": ""
},
{
"mobile": "050****88"
},
{
"opentimes": ""
},
{
"services": ""
},
{
"places": ""
},
{
"logo": null
},
{
"image": null
},
{
"video": ""
},
{
"owner_name": "Ben Brant"
},
{
"owners": "1"
},
{
"userpic": "http://graph.facebook.com/****/picture"
},
{
"circle": "3"
},
{
"fc": "0"
},
{
"rating_friends": ""
},
{
"rating_global": "3.3333"
},
{
"advice": ""
},
{
"subscription": "none"
}
]
},
{
"Business": [
{
"id": "5850"
},
{
"userid": ""
},
{
"name": "Bla Bla"
},
{
"description": ""
},
{
"address": ""
},
{
"email": "*****#gmail.com"
},
{
"phone2": ""
},
{
"phone3": ""
},
{
"mobile": "0*****995"
},
{
"opentimes": ""
},
{
"services": ""
},
{
"places": ""
},
{
"logo": null
},
{
"image": null
},
{
"video": ""
},
{
"owner_name": "Ben VBlooo"
},
{
"owners": "1"
},
{
"userpic": "http://graph.facebook.com/******/picture"
},
{
"circle": "3"
},
{
"fc": "0"
},
{
"rating_friends": ""
},
{
"rating_global": "2.0000"
},
{
"advice": ""
},
{
"subscription": "none"
}
]
},
{
"Info": {
"message": "No user for the business"
}
},
{
"OK": {
"message": "By Circle"
}
}
]
I'm trying to get the objects in javascript in this way but it doesnt work, should i loop through each Business object?? is there a way to access the real data objects directly?
Here's what I'm trying:
$.ajax({
type: 'POST',
url: 'BLABLA',
data: { BLABLA },
dataType: 'json',
success: function( resp ) {
if(resp.length == 0) {
$('.searchol').append('<li>No results found.</li>');
return;
}
$.each(resp, function(index, element) {
$('.searchol').append('Users Picture: '+element.Business.userpic);
But I cant seem to get to the object?

I just tried this code using your sample json like that
$.each(resp, function(index,element){
$.each(element, function(ind,ele){
if(ele.length){
$.each(ele,function(ind,ele){
if(ele.userpic)
console.log(ele.userpic)
})
}
})
})

"Business" is referring to an array (square bracket), so element.Business.userpic does not exist (element.Business[0].userpic exists though). Depending on what you want to achieve, you'll either have to loop through Business or access userpic of a particular array item.

Your business object is a array of object
"Business": [
{
"id": "5850"
},
Check this JSFiddle script on how to read that
Sample output
Picture: undefined (index):192
Picture: http://graph.facebook.com/****/picture

This will help you out
$.each(resp, function(index, element) {
$('.searchol').append('Users Picture: '+element.Business["userpic"]);

Your JSON is weird. Instead of :
Business : [
{ id : 'id1' }
{ name : 'name1' }
]
Business[0].id // access id
Business[1].name // access name
Where you have to remember where each attribute is in the array (or loop over the array to find it), you should have:
Business : {
id : 'id1',
name : 'name1'
}
Business.id // access id
Business.name // access name
If you can't change the JSON, you can use the following 2 methods to quickly get a property of Business:
var propMap = {
id : 0,
userid : 1,
name : 2 // etc
}
function getBusinessProp(business, prop) {
return business[propMap[prop]][prop];
}
// usage :
$('.searchol').append('Users Picture: '+ getBusinessProp(element.Business, 'userpic'));
If your array can be missing some items or the items can be in a different order for each business, then you need to iterate to find the property you're interested in:
function getBusinessProp(business, prop) {
for (var i=0; i<business.length; i++) {
if (business[i].hasOwnProperty(prop)) {
return business[i][prop];
}
}
}
// same usage, no need for the map anymore
The second method is probably better because it won't break if you change the order of the array or add new items in the array, etc and the performance boost given by using the map is probably not enough to justify the added maintenance cost.