Develop Reference

I want to create an object from an array which has subarray also

This is my input:
const arr = [10,20,[40,50,60],70,80,[90,100],111,112];
output what I want:
{10:10,20:20,'array1':{40:40,50:50,60:60},70:70,80:80,'array2':{90:90,100:100},111:111,112:112}

my approach using Array.prototype.reduce(). only handles 1 level nested array.
const arr = [10,20,[40,50,60],70,80,[90,100],111,112];
let count=1;
let a = arr.reduce((acc,curr) => {
if(Array.isArray(curr)){
let b = curr.reduce((acc1,curr1)=> {
acc1[curr1] = curr1;
return acc1
},{})
acc[`array${count}`] = b;
count+=1;
}
else{
acc[curr] = curr;
}
return acc;
},{})
console.log(a)
Since it is an object it necessarily doesn't have to be in the order you have given.

Simply loop through the array, formatting a new object as you go:
let array_count = 1;
let obj = {}
arr.forEach((el) => {
if(Number.isInteger(el)){
obj[el] = el;
} else {
inline_obj = {}
el.forEach((e2) => inline_obj[e2] = e2);
obj[`array${array_count}`] = inline_obj;
array_count += 1;
}
})

Here a recursive solution with reduce(), which also works for deeper nested arrays if you need that.
function foo(array){
let arrCounter=0;
return array.reduce((acc,curr)=>{
if(!Array.isArray(curr)) acc[curr]=curr
else{ arrCounter+=1;
acc[`array${arrCounter}`]=foo(curr)
}
return acc;
},{})
}
const arr = [10,20,[40,50,60],70,80,[90,100],111,112];
console.log(foo(arr));
const deepArr = [10,20,[40,50,60],70,80,[90,100,[40,50,60]],111,112];
console.log(foo(deepArr));

Javascript nested array: halve items and sum them up

I'm trying to create a function which returns me halve the data sumed up. I was able to do it on a non-nested Array but failing on the nested Array. I get the error Cannot read properties of undefined (reading 'push').
How the returned data should look like:
var data = [{"Key":1,"values":[
{"LastOnline":"21-11-29","Value":2},
{"LastOnline":"21-12-01","Value":2},
{"LastOnline":"21-12-03","Value":2}
]}];
What I have right now:
var data = [{"Key":1,"values":[
{"LastOnline":"21-11-28","Value":1},
{"LastOnline":"21-11-29","Value":1},
{"LastOnline":"21-11-30","Value":1},
{"LastOnline":"21-12-01","Value":1},
{"LastOnline":"21-12-02","Value":1},
{"LastOnline":"21-12-03","Value":1},
]}];
function halveMonth(data){
var newData = [];
var temp = [{"key":data.key,"values":[{}]}];
// sum 2 togheter
for(var i=1;i<data.values.length;i++){
if(data.values[i]){
temp.values[i].push({"LastOnline":data.values[i].LastOnline, "Value":(data.values[i].Value + data.values[[i-1]].Value)});
}
}
for(var i=0;i<temp.values.length;i++){
if(i % 2 == 0){
newData.push(temp.values[i]);
}
}
return newData;
}
console.log(halveMonth(data));

JS variables are case sensitive. Keep the key consistent everywhere. If you don't plan to use reduce here is the solution.
var data = [{"key":1,"values":[
{"LastOnline":"21-11-28","Value":1},
{"LastOnline":"21-11-29","Value":1},
{"LastOnline":"21-11-30","Value":1},
{"LastOnline":"21-12-01","Value":1},
{"LastOnline":"21-12-02","Value":1},
{"LastOnline":"21-12-03","Value":1},
]}];
function halveMonth(data){
let newData = []
for (let i = 0; i < data.length; i++) {
let temp = {"key":data[i].key,"values":[]}
for (let j = 0; j < data[i].values.length; j += 2) {
const res = (j+1===data[i].values.length) ? data[i].values[j].Value : data[i].values[j].Value + data[i].values[j+1].Value
temp.values.push({"LastOnline":(j+1===data[i].values.length)?data[i].values[j].LastOnline:data[i].values[j+1].LastOnline,"Value":res});
}
newData.push(temp);
}
return newData
}
console.log(halveMonth(data));

The variable data you declare at the first line of your snippet is an array. So you can't do data.values. You first need to indicate which index of your array you want to read. In this case : data[0].values

First things first, you data is itself an array - so assuming your real data has more than 1 element you'll need to do the same thing for each one.
It's helpful to start off with a method which does the work on just 1 element
const justASingle = {"Key":1,"values":[{"LastOnline":"21-11-28","Value":1},{"LastOnline":"21-11-29","Value":1},{"LastOnline":"21-11-30","Value":1},{"LastOnline":"21-12-01","Value":1},{"LastOnline":"21-12-02","Value":1},{"LastOnline":"21-12-03","Value":1}]};
function halveMonthSingle(data) {
return {
...data,
values: data.values.reduce((acc, item, idx) => {
if ((idx % 2) != 0)
acc.push({
...item,
Value: data.values[idx - 1].Value + item.Value
})
return acc;
}, [])
}
}
console.log(halveMonthSingle(justASingle))
Once you have that you can just use map do do it for every element
const data = [{"Key":1,"values":[{"LastOnline":"21-11-28","Value":1},{"LastOnline":"21-11-29","Value":1},{"LastOnline":"21-11-30","Value":1},{"LastOnline":"21-12-01","Value":1},{"LastOnline":"21-12-02","Value":1},{"LastOnline":"21-12-03","Value":1}]}];
function halveMonthSingle(data) {
return {
...data,
values: data.values.reduce((acc, item, idx) => {
if ((idx % 2) != 0)
acc.push({
...item,
Value: data.values[idx - 1].Value + item.Value
})
return acc;
}, [])
}
}
const result = data.map(halveMonthSingle)
console.log(result)

I would use reduce - saves me from trying to figure out why your two loops do not work other than data.values should be data[0].values
var data = [{"Key":1,"values":[{"LastOnline":"21-11-28","Value":1},{"LastOnline":"21-11-29","Value":1},{"LastOnline":"21-11-30","Value":1},{"LastOnline":"21-12-01","Value":1},{"LastOnline":"21-12-02","Value":1},{"LastOnline":"21-12-03","Value":1},]}];
const newArr = data.slice(0); // to not mutate original
newArr[0].values = data[0].values.reduce((acc,item,i) => {
if (i%2 !== 0) { // every second
acc.push(data[0].values[i]); // push the item
acc[acc.length-1].Value += data[0].values[i-1].Value; // add the first
}
return acc
},[])
console.log(newArr)

This works too. I basically did your idea, skipping the temp array and merging the two steps into one.
const data = [{"Key":1,"values":[
{"LastOnline":"21-11-28","Value":1},
{"LastOnline":"21-11-29","Value":1},
{"LastOnline":"21-11-30","Value":1},
{"LastOnline":"21-12-01","Value":1},
{"LastOnline":"21-12-02","Value":1},
{"LastOnline":"21-12-03","Value":1},
]}];
function halveMonth(data) {
const newData = [];
newData.push({
Key: data[0].Key,
values: []
});
for(let i = 0; i < data[0].values.length; i++){
if (i % 2 !== 0) {
newData[0].values.push({
LastOnline: data[0].values[i].LastOnline,
Value: data[0].values[i].Value + data[0].values[i-1].Value
});
}
}
return newData;
}
console.log(halveMonth(data));

Delete the previous and next element from an array while using array.map() in javascript

How can I delete the previous and next element from an array while using array.map();
In the code below, when I get to 'crossover' I want to delete both 'SUV' and 'sedan'.
The following code deletes 'sedan' and 'truck' instead of 'sedan' and 'SUV' ;
let arr = ['excavator','SUV','crossover','sedan','truck'] ;
arr = arr.map((ele,ind,ar) => {
if (ele === 'crossover'){
ar.splice(ind+1,1);
ar.splice(ind-1,1);
}
return ele + ": Sold.";
});
return arr; //it produces ['excavator: Sold.','SUV: Sold.','crossover: Sold.',,]

You can first remove the elements and then map the array, here is an example:
let arr = ['excavator','SUV','crossover','sedan','truck'];
arr.splice(arr.indexOf('crossover') - 1, 3, 'crossover');
arr = arr.map((ele) => {
return ele + ": Sold.";
});
console.log(arr);
The .splice(..) call replaces SUV, crossover and sedan with crossover

You should not remove elements on a .map interation since the array size will change as well as the array indexes.
You should try something like this:
let arr = ['excavator','SUV','crossover','sedan','truck'] ;
arr = arr.filter(element => element != "crossover");
arr = arr.map(ele => `${ele} :Sold.`);
console.log(arr);
Or, from an old school perspective:
let arr = ['excavator','SUV','crossover','sedan','truck'];
let newArr=[]
for (var i=0; i<arr.length; i++)
if(arr[i] !== 'crossover')
newArr.push(`${arr[i]} :Sold.`)
console.log(newArr);

itus has the correct anwer, IMO but for the sake of fun this is an alternative way:
let arr = ['excavator','SUV','crossover','sedan','truck'] ;
let suvIndex = null;
const result = arr.map((item, index) => {
if (item === "SUV") {
suvIndex = index;
}
if(suvIndex && index <= suvIndex + 2) {
return null;
}
return item;
}).filter(chunk => chunk)
console.log(result);
https://jsfiddle.net/vbz14fw6/

Create an arrays inside of another (main) array out of separated values

Problem
I have a string of numerical values separated by commas, and I want to include them in an array, and also each pair of them to be an array nested inside of the main array to be my drawing vertices.
How do I solve this problem?
Input:
var vertices = "24,13,47,20,33,9,68,18,99,14,150,33,33,33,34,15,91,10";
what I want them to be is:
Output:
var V_array = [[24,13],[47,20],[33,9],[68,18],[99,14],[150,33],[33,33],[34,15],[91,10]];

You could Split on every second comma in javascript and map the splitted pairs by converting the values to number.
var vertices = "24,13,47,20,33,9,68,18,99,14,150,33,33,33,34,15,91,10",
result = vertices.match(/[^,]+,[^,]+/g).map(s => s.split(',').map(Number));
console.log(result);

You can use the function reduce which operates over the splitted-string and check for the mod of each index.
let str = "24,13,47,20,33,9,68,18,99,14,150,33,33,33,34,15,91,10";
let result = str.split(',').reduce((a, s, i) => {
a.curr.push(Number(s));
if ((i + 1) % 2 === 0) {
a.arr.push(a.curr);
a.curr = [];
}
return a;
}, {arr: [], curr: []}).arr;
console.log(result);
.as-console-wrapper { max-height: 100% !important; top: 0; }

You can split string into array and use reduce method. Take a look at the code below
const vertices = "24,13,47,20,33,9,68,18,99,14,150,33,33,33,34,15,91,10";
const numbers = vertices.split(',').map(Number)
const res = numbers
.reduce((acc, number, index, srcArray) => {
if (index % 2) {
return acc
}
return [
...acc,
[ number, srcArray[index + 1] ],
]
}, [])
console.log(res)

My two cents :) [new version]
let
str = "24,13,47,20,33,9,68,18,99,14,150,33,33,33,34,15,91,10",
pair = [],
triplet = [];
JSON.parse(`[${str}]`).forEach((e,i)=>{pair.push( (i%2)?[pair.pop(),e]:e)})
console.log ( 'pair:', JSON.stringify(pair) )
// bonus => same idea for triplet :
JSON.parse(`[${str}]`).forEach((e,i)=>{
if ( (i%3)===2 ) triplet.push( [triplet.shift(),triplet.pop(),e] )
else if ( (i%3)===0 ) triplet.unshift(e)
else triplet.push(e)
})
console.log ( 'triplet:', JSON.stringify(triplet) )

You can use exec and JSON.parse
var vertices = "24,13,47,20,33,9,68,18,99,14,150,33,33,33,34,15,91,10";
var array1;
var reg = /[^,]+,[^,]+/g
let op = []
while((array1 = reg.exec(vertices))!== null){
op.push(JSON.parse(`[${array1[0]}]`))
}
console.log(op)

Split on the , and use Array.reduce to group the pair into a new 2-D array:
var vertices = "24,13,47,20,33,9,68,18,99,14,150,33,33,33,34,15,91,10";
const pair = vertices.split(",").reduce((acc, ele, idx, arr) => {
if(idx === 0 || idx%2 === 0) {acc.push([+ele, +arr[idx + 1]]);}
return acc;
}, []);
console.log(pair);
Same can be done using Array.map, if the index is odd skip the element and filter out the undefined elements:
var vertices = "24,13,47,20,33,9,68,18,99,14,150,33,33,33,34,15,91,10";
const pair = vertices.split(",").map((ele, idx, arr) => (idx === 0 || idx%2 === 0) ? [+ele, +arr[idx + 1]] : undefined).filter(e => e);
console.log(pair);

My two cents :)
( thanks to Code Maniac for the idea of using JSON.parse )
let str = "24,13,47,20,33,9,68,18,99,14,150,33,33,33,34,15,91,10";
let result = JSON.parse(`[${str}]`).reduce((acc, cur, i) => {
if (i===1) return [[acc,cur]]
if (i%2) acc.push( [acc.pop(), cur] )
else acc.push( cur )
return acc
});
console.log ( result )

Here is my solution.
var vertices = "24,13,47,20,33,9,68,18,99,14,150,33,33,33,34,15,91,10";
vertices = vertices.split(",");
function convertToMultiArray (arr, length) {
var nArr = [];
while(arr.length > 0) {
nArr.push(arr.splice(0,length));
}
return nArr;
}
const res = convertToMultiArray(vertices, 2);
console.log('res', res);

Get the index of a multidimensional array with the value of a given string in javascript

I have this array,
var arr = [["present",["John","Josh","Jay"]],["absent",["May","Mary","Mary Jane"]]];
var arr2 = [["J",["John","Josh","Jay"]],["M",["May","Mary","Mary Jane"]]];
And I want to get the data[0] of the array that have value of "Mary".
So in my example, value that I will get is "absent".
I want also to get the index of the array arr2 that have value of "Josh".
So in my second array, value that I will get is 0.
If possible to use underscore js, we can use it.
I tried to use _.contains() but failed.
Also these array is used in knockout js.

One other way of doing this job could be as follows;
var a1 = [["present",["John","Josh","Jay"]],["absent",["May","Mary","Mary Jane"]]],
a2 = [["J",["John","Josh","Jay"]],["M",["May","Mary","Mary Jane"]],["S",["Sally","Sam","Sammy Davis"]]],
getStatus = (a,n) => a.find(e => e[1].indexOf(n) !== -1)[0],
getIndex = (a,n) => a.findIndex(e => e[1].indexOf(n) !== -1);
console.log(getStatus(a1,"Mary"));
console.log(getIndex(a2,"Sammy Davis"));

var arr = [["present",["John","Josh","Jay"]],["absent",["May","Mary","Mary Jane"]]];
var arr2 = [["J",["John","Josh","Jay"]],["M",["May","Mary","Mary Jane"]]];
arr.forEach(function(e,i,a){
if(e[1].indexOf("Mary")>-1){
console.log(e[0])
}
});
arr2.forEach(function(e,i,a){
if(e[1].indexOf("Josh")>-1){
console.log(e[0])
}
});

First using filter() and second findIndex()
var arr = [["present",["John","Josh","Jay"]],["absent",["May","Mary","Mary Jane"]]];
var result1 = arr.filter(x => x[1].indexOf("Mary") !== -1)[0][0];
console.log(result1); // absent
var arr2 = [["J",["John","Josh","Jay"]],["M",["May","Mary","Mary Jane"]]];
var result2 = arr.findIndex(x => x[1].indexOf("Josh") !== -1);
console.log(result2); // 0

If your data set isn't really huge you can store two map objects in memory to quickly access values. Note that this won't work for duplicate names.
The benefit of this approach is that you only have to loop through each array once. If you use any method based on indexOf, you'll loop through your data every time you retrieve a value.
var arr = [["present",["John","Josh","Jay"]],["absent",["May","Mary","Mary Jane"]]];
var arr2 = [["J",["John","Josh","Jay"]],["M",["May","Mary","Mary Jane"]]];
var makeKeyMap = function(arr) {
return arr.reduce(function(map, data) {
data[1].forEach(function(key) {
map[key] = data[0];
});
return map;
}, {});
};
var makeIndexMap = function(arr) {
return arr.reduce(function(map, data, index) {
data[1].forEach(function(key) {
map[key] = index;
});
return map;
}, {});
};
var arrMap = makeKeyMap(arr);
var arr2Map = makeIndexMap(arr2);
console.log(arrMap["Mary"]);
console.log(arr2Map["Josh"]);
Edit: a performance test
var myTestData = createTestData();
var randomNameToFind = (function() {
var namesToFind = ["Aileen","Christina","Donna","Judith","Mandy","Sandra","Dawn","Tracey","Mhairi","Victoria","Carolyn","Gayle","Maria","Valerie"];
return function() {
return namesToFind[Math.floor(Math.random() * namesToFind.length)];
}
}());
console.log("Finding the number index for a random name out of 800 names, 10000 times:");
console.time("using index of approach");
var usingIndexOf = (a,n) => a.findIndex(e => e[1].indexOf(n) !== -1);
var results = [];
for (var i = 0; i < 10000; i += 1) {
results.push(usingIndexOf(myTestData, randomNameToFind()));
}
console.timeEnd("using index of approach");
console.time("using map approach");
var makeIndexMap = function(arr) {
return arr.reduce(function(map, data, index) {
data[1].forEach(function(key) {
map[key] = index;
});
return map;
}, {});
};
var myMap = makeIndexMap(myTestData);
results = [];
for (var j = 0; j < 10000; j += 1) {
results.push(myMap[randomNameToFind()]);
}
console.timeEnd("using map approach");
console.log("index map size: " + sizeof(myMap) + " bytes");
// Random data generation code below
function createTestData() {
var names = ["Nicola","Karen","Fiona","Susan","Claire","Sharon","Angela","Gillian","Julie","Michelle","Jacqueline","Amanda","Tracy","Louise","Jennifer","Alison","Sarah","Donna","Caroline","Elaine","Lynn","Margaret","Elizabeth","Lesley","Deborah","Pauline","Lorraine","Laura","Lisa","Tracey","Carol","Linda","Lorna","Catherine","Wendy","Lynne","Yvonne","Pamela","Kirsty","Jane","Emma","Joanne","Heather","Suzanne","Anne","Diane","Helen","Victoria","Dawn","Mary","Samantha","Marie","Kerry","Ann","Hazel","Christine","Gail","Andrea","Clare","Sandra","Shona","Kathleen","Paula","Shirley","Denise","Melanie","Patricia","Audrey","Ruth","Jill","Lee","Leigh","Catriona","Rachel","Morag","Kirsten","Kirsteen","Katrina","Joanna","Lynsey","Cheryl","Debbie","Maureen","Janet","Aileen","Arlene","Zoe","Lindsay","Stephanie","Judith","Mandy","Jillian","Mhairi","Barbara","Carolyn","Gayle","Maria","Valerie","Christina","Marion","Nicola","Karen","Susan","Claire","Fiona","Angela","Sharon","Gillian","Julie","Jennifer","Michelle","Louise","Lisa","Amanda","Donna","Tracy","Alison","Elaine","Jacqueline","Sarah","Caroline","Elizabeth","Laura","Lynn","Deborah","Lesley","Margaret","Joanne","Pauline","Lorraine","Carol","Kirsty","Yvonne","Lorna","Emma","Lynne","Tracey","Heather","Catherine","Pamela","Helen","Linda","Jane","Anne","Kerry","Suzanne","Wendy","Victoria","Diane","Mary","Dawn","Clare","Gail","Paula","Ann","Shona","Hazel","Christine","Andrea","Samantha","Marie","Lynsey","Sandra","Denise","Lee","Kelly","Gayle","Debbie","Jill","Kathleen","Patricia","Joanna","Catriona","Shirley","Ruth","Zoe","Leigh","Rachel","Melanie","Kirsteen","Aileen","Christina","Janet","Katrina","Stephanie","Audrey","Kirsten","Arlene","Maureen","Morag","Marion","Mhairi","Allison","Cheryl","Maria","Kim","Anna","Lindsay","Rebecca","Katherine","Mandy","Nicola","Karen","Claire","Angela","Fiona","Susan","Jennifer","Julie","Gillian","Michelle","Sharon","Sarah","Louise","Donna","Laura","Amanda","Alison","Lisa","Caroline","Kirsty","Jacqueline","Elaine","Lesley","Lynn","Deborah","Elizabeth","Joanne","Emma","Tracy","Lorraine","Lynne","Margaret","Heather","Carol","Lorna","Pauline","Kelly","Helen","Catherine","Linda","Victoria","Suzanne","Kerry","Pamela","Lee","Wendy","Jane","Yvonne","Tracey","Anne","Clare","Mary","Diane","Christine","Lynsey","Samantha","Shona","Andrea","Marie","Gail","Melanie","Dawn","Ann","Paula","Jill","Ruth","Leigh","Hazel","Debbie","Joanna","Denise","Lindsay","Gayle","Patricia","Catriona","Kathleen","Sandra","Leanne","Stephanie","Rachel","Katrina","Shirley","Kirsteen","Janet","Arlene","Zoe","Jillian","Anna","Judith","Mhairi","Natalie","Audrey","Carolyn","Morag","Aileen","Cheryl","Rebecca","Allison","Barbara","Mandy","Claire","Nicola","Karen","Angela","Gillian","Fiona","Jennifer","Laura","Susan","Julie","Michelle","Lisa","Sharon","Louise","Sarah","Tracy","Donna","Kelly","Kirsty","Amanda","Alison","Joanne","Caroline","Emma","Jacqueline","Elaine","Elizabeth","Lynne","Lesley","Deborah","Kerry","Victoria","Carol","Catherine","Lynn","Pauline","Margaret","Lorna","Lynsey","Lorraine","Linda","Suzanne","Tracey","Heather","Yvonne","Jane","Dawn","Mary","Helen","Anne","Wendy","Lee","Pamela","Jill","Lindsay","Clare","Christine","Diane","Leigh","Samantha","Shona","Joanna","Ruth","Debbie","Gail","Marie","Andrea","Paula","Kathleen","Catriona","Katrina","Denise","Melanie","Ann","Sandra","Gayle","Hazel","Jillian","Stephanie","Rachel","Kim","Natalie","Katherine","Patricia","Leanne","Cheryl","Mhairi","Morag","Arlene","Zoe","Kathryn","Aileen","Ashley","Judith","Anna","Frances","Janet","Lucy","Vicky","Christina","Kirsten","Rebecca","Nicola","Claire","Laura","Karen","Michelle","Louise","Jennifer","Fiona","Lisa","Gillian","Angela","Julie","Susan","Sarah","Kelly","Donna","Sharon","Emma","Caroline","Alison","Joanne","Tracy","Kirsty","Lynne","Amanda","Elaine","Jacqueline","Lesley","Kerry","Elizabeth","Lynn","Margaret","Deborah","Catherine","Heather","Lorna","Yvonne","Carol","Lorraine","Suzanne","Lynsey","Victoria","Helen","Linda","Pauline","Dawn","Anne","Jane","Tracey","Clare","Mary","Diane","Jill","Denise","Lee","Leanne","Christine","Shona","Pamela","Samantha","Paula","Joanna","Debbie","Stacey","Hazel","Cheryl","Lindsay","Gail","Rachel","Marie","Ann","Catriona","Andrea","Ruth","Kathryn","Katrina","Mhairi","Wendy","Leigh","Gayle","Melanie","Sandra","Stephanie","Anna","Jillian","Amy","Carolyn","Patricia","Carrie","Natalie","Kathleen","Lyndsey","Ashley","Rebecca","Vicky","Christina","Lindsey","Katherine","Arlene","Sara","Laura","Claire","Nicola","Lisa","Louise","Michelle","Fiona","Karen","Gillian","Jennifer","Emma","Angela","Susan","Kelly","Julie","Donna","Sarah","Kirsty","Sharon","Joanne","Amanda","Tracy","Alison","Elizabeth","Caroline","Elaine","Jacqueline","Lynne","Leanne","Deborah","Lesley","Lorraine","Victoria","Lynn","Pamela","Kerry","Lynsey","Lorna","Carol","Margaret","Heather","Helen","Catherine","Suzanne","Tracey","Yvonne","Cheryl","Linda","Pauline","Debbie","Jane","Dawn","Clare","Lindsay","M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var nameMap = names.reduce((map, n) => {
map[n[0]] = map[n[0]] || [];
map[n[0]].push(n);
return map;
}, {});
var testData = Object.keys(nameMap)
.sort()
.reduce((res, k) => {
res.push([k, nameMap[k]]);
return res;
}, []);
return testData;
};
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