Build a map using values of multiple objects in an array javascript - javascript

I need to build a map "A" from an existing array of objects. However the key value pairs on Map A are from the values of existing Object keys "id" and "cap".
Is it possible to read the values of 2 keys and store as an object
var items = [{
"id": 1,
"name": "Primary",
"cap": [{
"id": "1",
"name": "1s"
}, {
"id": "2",
"name": "T2s"
}]
},{
"id": 2,
"name": "Secondary",
"cap": [{
"id": "1",
"name": "1s"
}, {
"id": "2",
"name": "T2s"
}
]
}]
My map needs to be like this
{ "1" : [{
"id": "1",
"name": "1s"
}, {
"id": "2",
"name": "T2s"
}],
"2" : [{
"id": "1",
"name": "1s"
}, {
"id": "2",
"name": "T2s"
}]
}

Use Array#reduce to achieve the results like below:
var items = [{
"id": 1,
"name": "Primary",
"cap": [{
"id": "1",
"name": "1s"
}, {
"id": "2",
"name": "T2s"
}]
}, {
"id": 2,
"name": "Secondary",
"cap": [{
"id": "1",
"name": "1s"
}, {
"id": "2",
"name": "T2s"
}]
}];
var ans = items.reduce(function(v, i) {
v[i.id] = i.cap;
return v;
}, {});
console.log(ans);

You can do this using a simple loop on the original array, and defining a new key: value pair into the object.
// Create the map
var map = {}
// For every 'item' within the 'items' array
items.forEach(item => {
// Map the item ID to the item.cap array
map[item.id] = item.cap
}
var items = [{
"id": 1,
"name": "Primary",
"cap": [{
"id": "1",
"name": "1s"
}, {
"id": "2",
"name": "T2s"
}]
}, {
"id": 2,
"name": "Secondary",
"cap": [{
"id": "1",
"name": "1s"
}, {
"id": "2",
"name": "T2s"
}]
}]
var map = {}
items.forEach(item => {
map[item.id] = item.cap
})
console.log(map)

Using ES6 Array.from() method.
var items = [{
"id": 1,
"name": "Primary",
"cap": [{
"id": "1",
"name": "1s"
}, {
"id": "2",
"name": "T2s"
}]
},{
"id": 2,
"name": "Secondary",
"cap": [{
"id": "1",
"name": "1s"
}, {
"id": "2",
"name": "T2s"
}
]
}];
var obj = {};
var res = Array.from(items, x => obj[x.id] = x.cap);
console.log(obj);

Related

Transformation of nested object

I am new to JavaScript and Node JS
want to transform the following nested object with student
Data:
[{
"id": 1,
"name": "A",
"children": [{
"id": 2,
"name": "B",
"children": [{
"id": 3,
"name": "C"
},
{
"id": 4,
"name": "D"
}
]
}]
}]
to
Expected:
[{
"student": {
"id": 1,
"name": "A"
},
"children": [{
"student": {
"id": 2,
"name": "B"
},
"children": [{
"student": {
"id": 3,
"name": "C"
}
},
{
"student": {
"id": 4,
"name": "D"
}
}
]
}]
}]
I guess you are seeking a solution for an array with multiple student objects. So you can use the map method to modify them.
const original = [{
"id": 1,
"name": "A",
"children": [{
"id": 2,
"name": "B",
"children": [{
"id": 3,
"name": "C"
},
{
"id": 4,
"name": "D"
}
]
}]
}]
const modified = original.map(stu => {
return {
student: {
id: stu.id,
name: stu.name,
},
children: stu.children
}
})

how to fetch the single name property from nested array?

I am working on Angular Project, where i need to fetch name property from given nested array object.
I tried with lodash map function _.map('ArrayName',(o)=>o.name); here i am receving only [ Peter, Andy ] as result. I want all name property [Peter, Andy, Mills, mac, Teddy]like this. Can someone guide me how to do this.
[{
"id": "1",
"name": "Peter",
"children": []}
,{
"id": "2",
"name": "Andy",
"children": [
{
"id": "3",
"name": "Mills",
"children": []
},
{
"id": "4",
"name": "Mac",
"children": [
{
"id": "5",
"name": "Teddy",
"children": []
}
]
}
]}]
You'll need to access the nested children arrays recursively.
Here is an example using Array.prototype.flatMap() and spread syntax to recursively iterate each array of children and flatten the results.
const input = [{ "id": "1", "name": "Peter", "children": [] }, { "id": "2", "name": "Andy", "children": [{ "id": "3", "name": "Mills", "children": [] }, { "id": "4", "name": "Mac", "children": [{ "id": "5", "name": "Teddy", "children": [] }] }] }];
const recursivelyGetProp = (arr, prop) => (
arr.flatMap(({ children, [prop]: p }) =>
[p, ...(children.length ? recursivelyGetProp(children, prop) : [])]
));
console.log(recursivelyGetProp(input, 'name'));

Remove an associate object while looping through using map

I have a json array and i need to delete the subarray whose id value is 5, which is falling under the serialNo 1. I tried the following method, but its not deleting any entry in the subarray.
let Details = [
{ "serialNo": "1", "text": "AAA", "subArray": [{ "id": "1", "name": "geo" }, { "id": "5", "name": "gau" }, { "id": "4", "name": "joi" }] },
{ "serialNo": "2", "text": "BBB", "subArray": [{ "id": "7", "name": "rom" }, { "id": "5", "name": "dom" }, { "id": "4", "name": "noi" }] },
{ "serialNo": "3", "text": "CCC", "subArray": [{ "id": "1", "name": "glo" }, { "id": "5", "name": "gum" }, { "id": "4", "name": "lom" }] }
];
Details.map((data) => {
if (data.serialNo === "1") {
data.subArray.map((subDetails) => {
if (subDetails.id === "5") {
delete data.subArray[subDetails];
}
})
}
})
I don't know why you explicitely wants to use the map function. But the following works:
let Details = [
{ "serialNo": "1", "text": "AAA", "subArray": [{ "id": "1", "name": "geo" }, { "id": "5", "name": "gau" }, { "id": "4", "name": "joi" }] },
{ "serialNo": "2", "text": "BBB", "subArray": [{ "id": "7", "name": "rom" }, { "id": "5", "name": "dom" }, { "id": "4", "name": "noi" }] },
{ "serialNo": "3", "text": "CCC", "subArray": [{ "id": "1", "name": "glo" }, { "id": "5", "name": "gum" }, { "id": "4", "name": "lom" }] }
];
Details = Details.map(function (data) {
if (data.serialNo === "1") {
data.subArray = data.subArray.filter(function (sa) {
return (sa.id !== "5");
});
}
return data;
});
console.log(Details);
The first problem is that you're not returning anything from the map functions. The second problem is that data.subArray[subDetails] is undefined, subDetails is an object not an index in the data.subArray array. You can use a combination of map and filter to accomplished this instead of using delete.
let Details = [
{ "serialNo": "1", "text": "AAA", "subArray": [{ "id": "1", "name": "geo" }, { "id": "5", "name": "gau" }, { "id": "4", "name": "joi" }] },
{ "serialNo": "2", "text": "BBB", "subArray": [{ "id": "7", "name": "rom" }, { "id": "5", "name": "dom" }, { "id": "4", "name": "noi" }] },
{ "serialNo": "3", "text": "CCC", "subArray": [{ "id": "1", "name": "glo" }, { "id": "5", "name": "gum" }, { "id": "4", "name": "lom" }] }
];
Details.map((data) => {
if (data.serialNo === "1") {
data.subArray = data.subArray.filter((subDetails) => {
return subDetails.id !== "5";
})
}
return data;
});
console.log(Details);
If you want to stick with map what you need to do is to return undefined when subDetails.id is 5.
let Details = [
{ "serialNo": "1", "text": "AAA", "subArray": [{ "id": "1", "name": "geo" }, { "id": "5", "name": "gau" }, { "id": "4", "name": "joi" }] },
{ "serialNo": "2", "text": "BBB", "subArray": [{ "id": "7", "name": "rom" }, { "id": "5", "name": "dom" }, { "id": "4", "name": "noi" }] },
{ "serialNo": "3", "text": "CCC", "subArray": [{ "id": "1", "name": "glo" }, { "id": "5", "name": "gum" }, { "id": "4", "name": "lom" }] }
];
Details.map((data) => {
if (data.serialNo === "1") {
data.subArray = data.subArray.filter((subDetails) => {
return subDetails.id === "5" ? undefined : subDetails;
})
}
return data;
});
console.log(Details);
One map plus object constructor:
const arr = [
{ "serialNo": "1", "text": "AAA", "subArray": [{ "id": "1", "name": "geo" }, { "id": "5", "name": "gau" }, { "id": "4", "name": "joi" }] },
{ "serialNo": "2", "text": "BBB", "subArray": [{ "id": "7", "name": "rom" }, { "id": "5", "name": "dom" }, { "id": "4", "name": "noi" }] },
{ "serialNo": "3", "text": "CCC", "subArray": [{ "id": "1", "name": "glo" }, { "id": "5", "name": "gum" }, { "id": "4", "name": "lom" }] }
];
const s = 1, id = 5; // conditions
const r = arr.map(e => (e.serialNo == s)
? Object.assign(e, {'subArray': e.subArray.filter(a => a.id != id)})
: e);
console.log(JSON.stringify(r, null, 2));
Object.assign swaps old subArray with the new filtered one.

Javascript sum of items in a complex object

I have some data that I'm counting and putting the totals into an array.
Here is the data and code:
var data = {
"cars": [
{
"id": "1",
"name": "name 1",
"thsub": [
{
"id": "11",
"name": "sub 1",
"stats": {
"items": 5,
},
"ions": null
},
{
"id": "22",
"name": "sub 2",
"stats": {
"items": 5,
},
"translations": null
}
],
"image": null
},
{
"id": "2",
"name": "name 2",
"thsub": [
{
"id": "33",
"name": "sub 43",
"stats": {
"items": 20,
},
"ions": null
},
{
"id": "44",
"name": "sub 76",
"stats": {
"items": 5,
},
"translations": null
}
],
"image": null
}
]
}
var thCount = [];
for(key in data.cars[0].thsub ){
if(data.cars[0].thsub[key].stats){
thCount.push(data.cars[0].thsub[key].stats.items);
}
}
console.log(thCount);
For some reason "thCount" is returning [5, 5] when the result should be: [10, 25]
where is the code going wrong?
The correct code for your problem is as pasted below:
**var count = [];
for(var i = 0; i < data.cars.length; i++){
countSum = 0;
for(key in data.cars[i].thsub){
countSum = countSum + data.cars[i].thsub[key].stats.items;
}
count.push(countSum);
}**
Try this code, will solve your problem.
You need another loop on cars.
var data = {
"cars": [{
"id": "1",
"name": "name 1",
"thsub": [{
"id": "11",
"name": "sub 1",
"stats": {
"items": 5,
},
"ions": null
}, {
"id": "22",
"name": "sub 2",
"stats": {
"items": 5,
},
"translations": null
}],
"image": null
},
{
"id": "2",
"name": "name 2",
"thsub": [{
"id": "33",
"name": "sub 43",
"stats": {
"items": 20,
},
"ions": null
}, {
"id": "44",
"name": "sub 76",
"stats": {
"items": 5,
},
"translations": null
}],
"image": null
}
]
}
var thCount = [];
for (var l = 0, m = data.cars.length; l < m; l++) {
thCount[l] = 0;
for (var i = 0, j = data.cars[l].thsub.length; i < j; i++) {
if (data.cars[l].thsub[i].stats) {
thCount[l]+=data.cars[l].thsub[i].stats.items;
}
}
}
console.log(thCount);
You should use reduce() and map() methods.Any of this using a callback function.
The reduce() method applies a function against an accumulator and each
value of the array (from left-to-right) to reduce it to a single
value.
The map() method creates a new array with the results of calling a
provided function on every element in this array.
var result=data.cars.map(function(item){
return item.thsub.reduce(function(a, b) { return a.stats.items + b.stats.items; });
});
var data = {
"cars": [
{
"id": "1",
"name": "name 1",
"thsub": [
{
"id": "11",
"name": "sub 1",
"stats": {
"items": 5,
},
"ions": null
},
{
"id": "22",
"name": "sub 2",
"stats": {
"items": 5,
},
"translations": null
}
],
"image": null
},
{
"id": "2",
"name": "name 2",
"thsub": [
{
"id": "33",
"name": "sub 43",
"stats": {
"items": 20,
},
"ions": null
},
{
"id": "44",
"name": "sub 76",
"stats": {
"items": 5,
},
"translations": null
}
],
"image": null
}
]
}
console.log(data.cars.map(function(item){
return item.thsub.reduce(function(a, b) { return a.stats.items + b.stats.items; });
}));

Underscore Create array of objects from JSON object

I have following JSON structure:
{
"shops": {
"categories": {
"cat_1": {
"id": "1",
"label": "Men's Fashions",
"Brands": [{
"id": "2",
"name": "Smith"
}]
},
"cat_2": {
"id": "2",
"label": "Restaurants",
"Brands": [{
"id": "3",
"name": "KFC"
}, {
"id": "4",
"name": "SUBWAY"
}, {
"id": "5",
"name": "MLD"
}, {
"id": "6",
"name": "THAI"
}]
},
"cat_3": {
"id": "3",
"label": "Specialty Shops",
"Brands": [{
"id": "7",
"name": "BODY SHOP"
}]
}
}
}
}
I'd like to achieve something like this:
[{
"categoryid": "1",
"id": "2",
"label": "Men's Fashions",
"name": "Smith"
},
{
"categoryid": "2",
"id": "3",
"label": "Restaurants",
"name": "KFC"
},
{
"categoryid": "2",
"id": "4",
"label": "Restaurants",
"name": "SUBWAY"
},
{
"categoryid": "2",
"id": "5",
"label": "Restaurants",
"name": "MLD"
},
{
"categoryid": "2",
"id": "6",
"label": "Restaurants",
"name": "THAI"
}, {
"categoryid": "3",
"id": "7",
"label": "Specialty Shops",
"name": "BODY SHOP"
},
]
Is there an elegant way to achieve it using underscore?
I tried to use nested _.each() to do that, but feel there might be something better.
generateArray: function(obj) {
var newResult = [];
_.each(obj.categories, function(c) {
_.each(c.Brands, function(d) {
newResult.push({
"categoryid": c.id,
"id": d.id,
"label": c.label,
"name": d.name
});
});
});
return newResult;
}
Anyone can advise me which way is more efficiency at running time?
mine or #Artyom Neustroev or #Anthony Chu ?
You don't really need underscore for that task. Use simple for .. in .. and for (...) loops:
var json = {...};
var result = [];
for (var catKey in json.shops.categories) {
var currentCategory = json.shops.categories[catKey];
for (var i = 0; i < currentCategory.Brands.length; i++) {
var currentBrand = currentCategory.Brands[i];
result.push({
categoryid: currentCategory.id,
label: currentCategory.label,
id: currentBrand.id,
name: currentBrand.name
});
}
}
Fiddle here
Instead of each()'s, here's a way to do it with map()'s...
var output = _.chain(input.shops.categories)
.map(function (category) {
return _(category.Brands).map(function (brand) {
return { categoryId: category.id,
id: brand.id,
label: category.label,
name: brand.name
};
});
}).flatten().value();
JSFIDDLE

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