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Get Key Value pair after String Split

I have a string in the form
Key=asdf, num=90, Key=ert, num=20, Key=yged, num=20, Key=kned, num=35
I have to filter only Key num pairs which has value 20 and store them into a Key Value pair such that Key=ert, num=20 will be first record and Key=yged, num=20 will be second record so on. How can I use Map in JavaScript so that always first value will go as key and second will go as value and form pairs in this case. I have used the following :
var dataString = JSON.parse(data).data;
var arrayVal = new Array();
arrayVal = dataString.split(', ');
for(a in arrayVal){
console.log(arrayVal[a]);
}

Array.map probably isn't the best tool for the job here. Array.reduce would be a better approach. Since you know what your delimiters are (namespaces and equal signs), you can logically split things up so that you know that every other iteration will give you a key/value. You can then create a mechanism to track what the last key is so you can map the value to it.
const str = 'Key=asdf, num=90, Key=ert, num=20, Key=yged, num=20, Key=kned, num=35';
const arr = str.split(', ').reduce( (acc, curr) => {
const entry = curr.split('=');
const key = entry[0];
const val = entry[1];
if (key === 'Key') {
acc['last_key'] = val
acc[val] = null;
} else if (key === 'num') {
acc[acc['last_key']] = val;
}
return acc;
}, {});
delete arr.last_key;
console.log(arr);

Here you go. It's kinda ugly.
let result = dataString.split(', ')
.map((value, index, array) =>
value === 'num=20' && array[index - 1])
.filter(x => x);
console.log(result);

Here's my say
const dataString = JSON.parse(data).data;
const arrayVal = dataString.split(', ');
const obj = {}; // initialize the object
for (let i = 0; i < arrayVal.length; i += 2) { // Iterating over two elements for the key and value
const key = arrayVal[i].split('=')[1];
const value = arrayVal[i + 1].split('=')[1];
obj[key] = value;
}
console.log(obj);

How to check if object with no names exists in array?

I am building a javascript function where I want to add an object to an array IF it is not already present, if it is I just want to update value.
My objects look like this:
[{31652237148248: 12}, {4365124714824: 4}]
How can I check the Array if there is an object with the ID of 31652237148248?
I tried this but it did not work:
var index = cartItems.findIndex((obj => obj[id] == id));

Use the in operator to check if the id is a property of the object:
const cartItems = [{31652237148248: 12}, {4365124714824: 4}];
const id = '4365124714824';
const index = cartItems.findIndex((obj => id in obj));
console.log(index);

You are looking to see if the value of objects property is equal to the id. 31652237148248 is never going to equal 12
so you can just do a type of
var index = cartItems.findIndex(obj => typeof obj[id] !== undefined);
you can do a truthy check - will fail if it is a falsey value.
var index = cartItems.findIndex(obj => obj[id]);
you can use object keys and includes or if first is equal
var index = cartItems.findIndex(obj => Object.keys(obj).includes(id));
var index = cartItems.findIndex(obj => Object.keys(obj)[0] === id);
A bunch of ways to do it
Personally a better way is just to use an object and not an array for the data.
var items = {31652237148248: 12, 4365124714824: 4}
const addItem = (id, count) => {
cartItems[id] = (cartItems[id] || 0) + count
}
const getArray = () =>
Object.entries(items).map(([key, count]) => ({ [key]: count }))

Try
let add = (obj,arr,k=Object.keys(obj)[0]) =>
arr.some( o=> (k in o)&&(o[k]=obj[k]) ) || arr.push(obj)
let data = [{31652237148248: 12}, {4365124714824: 4}]
let add = (obj,arr,k=Object.keys(obj)[0]) =>
arr.some( o=> (k in o)&&(o[k]=obj[k]) ) || arr.push(obj)
// TEST
add({31652237148248: 15}, data);
console.log('update',data);
add({666: 15}, data);
console.log('add',data);

iterate through nested array to match IDs

I have a set of data which is nested arrays, these arrays may be empty or they may infact contain an ID, if one of the arrays ID's matches the ID im comparing it with, I want to take all of the data inside that array which matched and assign it to a variable to be used...
example:
data = [[],[],[],[],[],[],[],[],[{"id":"123","name":"DARES HOUSE 2019","startDate":null,"endDate":null,"country":null,"city":null,"type":"Event","members":null}],[],[],[],[],[],[],[],[],[],[],[]]
id = 123
matchedArray =
for (var i = 0; i < potentialEvents.length; i++) {
for (var j = 0; j < potentialEvents[i].length; j++) {
if (id === potentialEvents[i].id) {
return;
}
}
}
console.log(matchedArray)
I'm trying to have it so matchedArray will be the array with thhe matched IDs!!
if you can help, thank you a lot!

You can do this with a combination of .map, .filter and .flat
var data = [[],[],[],[],[],[],[],[],[{"id":"123","name":"DARES HOUSE 2019","startDate":null,"endDate":null,"country":null,"city":null,"type":"Event","members":null}],[],[],[],[],[],[],[],[],[],[],[]]
var id = 123;
var matchedArray = data.map( arr => {
return arr.filter(x => x.id == id);
}).flat();
console.log(matchedArray);

You can use Array#filter method to filter the inner array and Array#flatMap method to concatenate filtered array into one.
let data = [[],[],[],[],[],[],[],[],[{"id":"123","name":"DARES HOUSE 2019","startDate":null,"endDate":null,"country":null,"city":null,"type":"Event","members":null}],[],[],[],[],[],[],[],[],[],[],[]];
let id = 123;
let matchedArray = data.flatMap(arr => arr.filter(obj => obj.id == id))
console.log(matchedArray)

I'd recommend to use .some rather then .filter/.map/.flatMap. The main benefit is that it allows to stop traversing array when element is found.
On big arrays with a lot of data it will be more efficient (≈50 times faster): jsperf test
const data = [[],[],[],[],[],[],[],[],[{"id":"123","name":"DARES HOUSE 2019","startDate":null,"endDate":null,"country":null,"city":null,"type":"Event","members":null}],[],[],[],[],[],[],[],[],[],[],[]]
const id = 123;
let matchedArray = null;
data.some((a) => {
return a.some((v) => {
if (v != null && v.id == id) {
matchedArray = a;
return true;
}
});
});
console.log(matchedArray);

Find the first unique value in an array or string

How can I get one unique value in an array or string? Only the first value. Pure JS only.
My example:
function searchValue () {
let inputText = [1,1,4,2,2,2,3,1];
let foundedValue;
for (let i = 0; i < inputText.length; i++) {
if (i === inputText.indexOf(inputText[i]) && i === inputText.lastIndexOf(inputText[i])) {
foundedValue = inputText[i];
break;
} else {
foundedValue = "not founded.";
}
}
return foundedValue;
}
console.log("Search value: "+ searchValue())
Answer is 4.
But, I need a short solution. Using the find() and filter() functions.

You can find the first unique item in your array using find() and comparing indexOf() to lastIndexOf() to determine whether or not there is more than one instance of an item in the array. If you need to find unique characters in a string, then you can first split it into an array and then use the same approach.
const arr = [1, 1, 4, 2, 2, 2, 3, 1];
const result = arr.find((x) => arr.indexOf(x) === arr.lastIndexOf(x));
console.log(result);
// 4
const text = 'aadbbbca';
const textarr = text.split('');
const textresult = textarr.find((x) => textarr.indexOf(x) === textarr.lastIndexOf(x));
console.log(textresult);
// d

You can try this.
const arr = [1, 1, 4, 2, 2, 2, 3, 1];
let r = {};
arr.map(a => r[a] = (r[a] || 0) +1)
var res = arr.find(a => r[a] === 1 )
console.log(res)

You can use js Set() object.
At first you could create a Set of duplicated elements.
const inputText = [1,1,4,2,2,2,3,1];
const duplicatesSet= inputText.reduce((dupSet, el) =>
inputText.filter(arrEl => arrEl === el).length > 1 ?
dupSet.add(el) : dupSet
, new Set());
Second you could use array.find. It returns first duplicated element.
const firstDupElement = inputText.find(el => duplicatesSet.has(el));

const searchValue = (_param) => {
for (let i= 0; i < _param.length; i+= 1) {
if (_param.indexOf(_param[i]) === _param.lastIndexOf(_param[i])) return _param[i];
}
return "not founded.";
}

let arr = [1,1,2,2,2,1,3,1,4,4,5]
const dupelearray = (array) => {
let arr2 =[...arr]
let ele = []
let state = false
arr2.map((i,index)=>{
arr2.splice(index,1)
arr.map((j)=>{
return arr2.includes(j) ? null : state=true
})
state && ele.push(i)
state=false
arr2.splice(index,0,i)
})
return console.log(arr.indexOf(ele[0]))
}
dupelearray(arr)
wow i didnt knew lastindexof method and was making this algo so difficult
btw this solution also works but definitely i am new in algo so this will take much more time but the solution still works!!!!!! damn should remember more methods or you have to think so much -_-

ES6 Array methods to remove / detect duplicate objects in an array

I am trying to add an object to an array if the array already does not have that object.
So I have an array as follows
[{id:1},{id:2},{id:3}]
I want to check if a id:1 exist or not if not then add if yes then show an error or log a message.
I am able to achieve this using a simple array as follows.
let result =[1,2,2,3,1,4,1,4,2,3].filter((el, i, a) => i === a.indexOf(el));
I cannot figure out how to achive the same with array of objects.
Thanks

You can use some to check for duplicates like:
// array with duplicate objects {id:1}
let arr = [{id:1},{id:1},{id:2}]
function duplicateFound(arr){
const ids = arr.map(x => x.id);
return ids.some((item, idx) => ids.indexOf(item) != idx);
}
console.log(duplicateFound(arr));
// array with not duplicates
arr = [{id:1},{id:2},{id:3}]
console.log(duplicateFound(arr));

You can use Array#filter, and check the length:
const arr = [{id:1},{id:2},{id:3}];
const el = { id: 1 };
const exists = arr.filter(({ id }) => id === el.id).length > 0;
console.log(exists);
Or you can use Array#find, which has a slight advantage over Array#filter, since it will stop as soon as an item was found.
const arr = [{id:1},{id:2},{id:3}];
const el = { id: 1 };
const exists = !!arr.find(({ id }) => id === el.id);
console.log(exists);
You can wrap your array with a proxy that has a set trap, to prevent the insertion of duplicates automatically:
const arr = [{id:1},{id:2},{id:3}];
const arrayChangeHandler = {
set: function(target, property, value, receiver) {
if(property === 'length') {
return true;
}
const exists = !!target.find(({ id }) => id === value.id);
if(exists) {
console.log(`Id: ${value.id} exists!`); // you can return false here, and it will throw an error
} else {
target.push(value);
}
return true;
}
};
const pArr = new Proxy(arr, arrayChangeHandler);
pArr.push({ id: 1 });
pArr.push({ id: 10 });
console.log(JSON.stringify(arr));

You could try inserting all values as keys to a new array then flip keys & vals
let arr = "abccba".split('');
let res = [];
arr.forEach((n) => {
res[n] = n;
});
console.log(Object.keys(res));
A concern might be that if your values are numbers then you might need to recast them eg.
res = res.map(n) => +n