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filter array of ojects with max value in javascript

Hi I have an array of objects like below:
let tbrows = [{"rowindx":0,"speciescnt":2},{"rowindx":0,"speciescnt":3},{"rowindx":1,"speciescnt":2},{"rowindx":1,"speciescnt":3}]
I want to get the maximum value of speciecnt for each row (i.e. after filtering the array) I would like it to be
let tbrows = [{"rowindx":0,"speciescnt":3},{"rowindx":1,"speciescnt":3}];
I am using the following code that I found on the web to filter an array but it only filters on one attribute of object.
const max2 = tbrows.reduce((op, item) => op = op > item.speciescnt? op : item.speciescnt, 0);

You can also using reduce() to do it
let tbrows = [{"rowindx":0,"speciescnt":2},{"rowindx":0,"speciescnt":3},{"rowindx":1,"speciescnt":2},{"rowindx":1,"speciescnt":3}]
let result = tbrows.reduce((a,c) => {
let obj = a.find(i => i.rowindx == c.rowindx)
if(!obj){
a.push(c)
}else if(c.speciescnt > obj.speciescnt){
obj.speciescnt = c.speciescnt
}
return a
},[])
console.log(result)

Turn the array into an object (right now, you're trying to turn it into just a number). Have the object be indexed by the row index, with the associated value for that row as the highest speciecnt found so far. Then you can turn the object back into an array.
const input = [{"rowindx":0,"speciescnt":2},{"rowindx":0,"speciescnt":3},{"rowindx":1,"speciescnt":2},{"rowindx":1,"speciescnt":3}];
const grouped = {};
for (const { rowindx, speciescnt } of input) {
grouped[rowindx] = Math.max(grouped[rowindx] ?? -Infinity, speciescnt);
}
const output = Object.entries(grouped)
.map(([rowindx, speciescnt]) => ({ rowindx, speciescnt }));
console.log(output);

Find Unique value from an array based on the array's string value (Javascript)

so I want to find unique values from an array.
so for example I have this array:
const mainArr = ['shape-10983', 'size-2364', 'size-7800', 'size-4602', 'shape-11073', 'size-15027', 'size-15030', 'size-15033', 'height-3399', 'height-5884']
so I want to find the first matching value for each unique item.
for example, in the array, I have two strings with the shape prefix, six items with the size prefix, and two items with the height prefix.
so I want to output to be something like
const requiredVal = ["shape-10983", "size-2364", "height-3399"]
I want only the first value from any set of different values.

the simplest solution will be to iterate on the list and storing what you got in a dictionary
function removeSimilars(input) {
let values = {};
for (let value of input) {//iterate on the array
let key = value.splitOnLast('-')[0];//get the prefix
if (!(key in values))//if we haven't encounter the prefix yet
values[key] = value;//store that the first encounter with the prefix is with 'value'
}
return Object.values(values);//return all the values of the map 'values'
}
a shorter version will be this:
function removeSimilars(input) {
let values = {};
for (let value of input)
values[value.splitOnLast('-')[0]] ??= value;
return Object.values(values);
}

You could split the string and get the type and use it aks key for an object along with the original string as value. At result take only the values from the object.
const
data = ['shape-10983', 'size-2364', 'size-7800', 'size-4602', 'shape-11073', 'size-15027', 'size-15030', 'size-15033', 'height-3399', 'height-5884'],
result = Object.values(data.reduce((r, s) => {
const [type] = s.split('-', 1);
r[type] ??= s;
return r;
}, {}));
console.log(result);

If, as you mentioned in the comments, you have the list of prefixes already available, then all you have to do is iterate over those, to find each first element that starts with that prefix in your full list of possible values:
const prefixes = ['shape', 'size', 'height'];
const list = ['shape-10983', 'size-2364', 'size-7800', 'size-4602', 'shape-11073', 'size-15027', 'size-15030', 'size-15033', 'height-3399', 'height-5884']
function reduceTheOptions(list = [], prefixes = [], uniques = []) {
prefixes.forEach(prefix =>
uniques.push(
list.find(e => e.startsWith(prefix))
)
);
return uniques;
}
console.log(reduceTheOptions(list, prefixes));

Try this:
function getRandomSet(arr, ...prefix)
{
// the final values are load into the array result variable
result = [];
const randomItem = (array) => array[Math.floor(Math.random() * array.length)];
prefix.forEach((pre) => {
result.push(randomItem(arr.filter((par) => String(par).startsWith(pre))));
});
return result;
}
const mainArr = ['shape-10983', 'size-2364', 'size-7800', 'size-4602', 'shape-11073', 'size-15027', 'size-15030', 'size-15033', 'height-3399', 'height-5884'];
console.log("Random values: ", getRandomSet(mainArr, "shape", "size", "height"));

I modified the #ofek 's answer a bit. cuz for some reason the ??= is not working in react project.
function removeSimilars(input) {
let values = {};
for (let value of input)
if (!values[value.split("-")[0]]) {
values[value.split("-")[0]] = value;
}
return Object.values(values);
}

create a new array and loop over the first array and check the existing of element before in each iteration if not push it to the new array

Jquery check if one array contains same value

I have an simple javascript array that may contain duplicates or maynot contain duplicates.
var names = [
['aaa','pin/test1.html'],
['bbb','pin/test2.html'],
['ttt','test.html'],
['ggg','test.html'],
['yyy','un/777.html'],
['ggg','test3.html'],
['nnn','test3.html'],
['eee','n/777.html'],
['sss','pin/test1.html'],
['xxx','pin/test2.html'],
['ppp','pin/test1.html'],
];
I need to find the duplicate filepath and put their name into new array. If there is no duplicate then assign its name in first and then assign '' after two values. I could point all the codes that I have tried but it doesnt work. I accept jquery solution also. The expected outcome is this.
var outcome = [
[['aaa','sss','ppp'], 'pin/test1.html'],
[['bbb','eee','xxx'], 'pin/test2.html'],
[['ttt','ggg',''], 'test.html'],
[['yyy','',''], 'un/777.html'],
[['ggg','nnn',''], 'test3.html'],
];
What I have tried is this
for (var i = 0; i < arr.length; i++) {
var uniqueNames = [];
$.each(arr[i], function (i, el) {
if ($.inArray(el, uniqueNames) === -1) uniqueNames.push(el);
});
console.log(uniqueNames);
}

You could take a hash table and an array of empty strings and find the next slot for the value.
The array is reduced by taking an object as accumulator and a destructure array as value (the first part of the array) and key (the second part, aka filepath).
Inside of Array#reduce, a property check with the key is made and if undefined, an array with the wanted structure (array with two items, the first is an array with three emty spaces and the key) is being assigned by using a logical nullish assignment ??=.
The next line assigns the value to the next free slot, an item with an empty string.
Finally the accumulator is returned.
To get only an array as result, a conversion of the values of the object takes place.
let names = [['aaa','pin/test1.html'], ['bbb','pin/test2.html'], ['ttt','test.html'], ['ggg','test.html'], ['yyy','un/777.html'], ['ggg','test3.html'], ['nnn','test3.html'], ['eee','n/777.html'], ['sss','pin/test1.html'], ['xxx','pin/test2.html'], ['ppp','pin/test1.html']],
grouped = Object.values(names.reduce((r, [v, k]) => {
r[k] ??= [Array(3).fill(''), k];
r[k][0][r[k][0].indexOf('')] = v;
return r;
}, {}));
console.log(grouped);
.as-console-wrapper { max-height: 100% !important; top: 0; }

const aux = (names) => {
const hash = {};
let max = 0;
names.forEach(ele => {
if (!hash[ele[1]]) hash[ele[1]] = [];
hash[ele[1]].push(ele[0]);
max = Math.max(hash[ele[1]].length, max);
});
return Object.keys(hash).map(ele => [[...hash[ele], ...Array(max -hash[ele].length).fill("")], ele]);
}
var names = [
['aaa','pin/test1.html'],
['bbb','pin/test2.html'],
['ttt','test.html'],
['ggg','test.html'],
['yyy','un/777.html'],
['ggg','test3.html'],
['nnn','test3.html'],
['eee','n/777.html'],
['sss','pin/test1.html'],
['xxx','pin/test2.html'],
['ppp','pin/test1.html'],
];
console.log(aux(names))
This might help

You do not need jQuery for dealing with regular JS structure, you can achieve what you want with a simple code like this:
var names = [['aaa','pin/test1.html'],['bbb','pin/test2.html'],['ttt','test.html'],['ggg','test.html'],['yyy','un/777.html'],['ggg','test3.html'],['nnn','test3.html'],['eee','n/777.html'],['sss','pin/test1.html'],['xxx','pin/test2.html'],['ppp','pin/test1.html'],];
let lengthToFill = 0;
// collecting all the duplicates into a map
const pathMap = {};
names.forEach(name => {
// just in case if you're not familiar with array destructuring
// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Destructuring_assignment
const [pathName, path] = name;
// make sure we have an array to deal with
// just in case you're not familiar with Nullish coalescing operator (??)
// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Nullish_coalescing_operator
pathMap[path] = pathMap[path] ?? [];
pathMap[path].push(pathName);
// tracking the max number of elements we're adding into a single entry
lengthToFill = Math.max(lengthToFill, pathMap[path].length);
});
const result = Object.entries(pathMap).map(entry => {
// constructing new array entry based on the data we've collected so far
return [
entry[1].concat(Array(lengthToFill - entry[1].length).fill('')),
entry[0],
];
});
console.log(result);
This solution will work for any number of elements that you'd like to fill the array with ''. It makes sure that the length of final listing is the same for all entries.

how to store many arrays to one key

I just get starting learning JS recently. Now I came across the problem and could not find blogs or tutorial to help very much or I did not get their points!
My problems is how to store many arrays to one key:
My code here:
let lines = fs.readFileSync(inGff).toString().split("\n");
...
let column = lines[i].toString().split("\t");
id = clpP1_69910 or clpP1_54343 or clpP1_69554 ...
obj[id] = column; //only work for one key to one array.
In fact. I can do it simply with Perl:
push #{$obj{$id}}, [#info]
Not sure if there is a similar utility or more advanced in JS. Any suggestions are welcome. Thanks!
enter image description here

You can store arrays inside objects like so:
let data = {};
let keys = ['clpP1_69910', 'clpP1_69915', 'clpP1_69920', 'clpP1_69925'];
// Iterate keys
keys.forEach(el => {
let arr = [];
// Iterate to push array items
for (let i = 0; i < 10; i++) {
arr.push(i);
}
// Assign array to key
data[el] = arr;
// Clear array
arr = null;
});
console.log(data);

Keys can store any type of value
To solve this you should set clpP1_69910 to an empty Array and .push to the array when you add a column.
obj[clpP1_69910] = []
const lines = fs.readFileSync(inGff).toString().split('\n')
const columns = lines.map(line => line.toString().split('\t'))
columns.forEach(column => obj[clpP1_69910].push(column))
Or, the short version:
obj[clpP1_69910] = fs.readFileSync(inGff).toString().split('\n').map(line => line.toString().split('\t')).reduce((acc, cur) => acc.concat(cur), [])
The last part, the .reduce section, flattens the array of arrays, returning all the columns.

Remove last letter from map value

So I'm getting this from backend:
{"Item":{"userEmail":"b","Username":"bUsername","Push":"sdsdsd","Password":"sdsds","Buddy":{"datatype":"SS","contents":{"Drake":"Drake","Ola":"Ola","b":"b","d":"d"}}}}
I use Object.Keys to narrow down the contents to:
Drake,Ola,b,d
Which I then map to give:
[{"id":"Drake"},{"id":"Ola"},{"id":"b"},{"id":"d"}]
Which is then used on my Angular Front-end as .id. I want to remove the last letter from each value i.e leaving Drak,Ol etc. I've tried many ways but have failed, how can I achieve this please so that the id has those values?
EDIT
I also want to now get that value that was cut AND add it such that the end product will be [{"id":"Drak",valueThatWasCut:"e"}]

You could iterate the object's keys and build with the short string a new object.
var data = {"Item":{"userEmail":"b","Username":"bUsername","Push":"sdsdsd","Password":"sdsds","Buddy":{"datatype":"SS","contents":{"Drake":"Drake","Ola":"Ola","b":"b","d":"d"}}}},
ids = Object.keys(data.Item.Buddy.contents).reduce(function (r, k) {
var n = k.slice(0, -1);
return n ? r.concat({ id: n }) : r;
}, []);
console.log(ids);

Perhaps something like :
var arr = [{"id":"Drake"},{"id":"Ola"},{"id":"b"},{"id":"d"}];
var result = arr.map(x => x.id.slice(0,-1));
console.log(result); // [ 'Drak', 'Ol', '', '' ]

Create a temporary contents object and change in that.
Then just set this in the original object. ES6 spread operators would save the rest of data without respecifying all keys and values.
let items = {"Item:{"userEmail":"b","Username":"bUsername","Push":"sdsdsd","Password":"sdsds","Buddy":{"datatype":"SS","contents":{"Drake":"Drake","Ola":"Ola","b":"b","d":"d"}}}};
let contents = items.Item.Buddy.contents;
let contentsNew = Object.keys(contents).map((content) => {
return {[content.substring(0, content.length-1)]: content.substring(0, content.length-1), valueThatWasCut: content[content.length-1]};
});
items = {...items, Item: {...items.Item,Buddy:{...items.Item.Buddy,contents: contentsNew}}};
console.log(items);