javascript - comparing arrays elements

Question

I've got an array that could have 4 digits elements or less (from html select) for example some possible variants of myArray:

myArray = ['1']
myArray = ['4'] 
myArray = ['2', '3']
myArray = ['1', '2', '3', '4'] 
etc...

now I've got an object that has possible variants of myArray for example some possible variants of myObject:

myObject = [
   {active: false, forArrays:['2','4']},
   {active: false, forArrays:['2,3,4','2,4']},
   {active: false, forArrays:['2','1,4']},
   {active: false, forArrays:['2']},
]

I want to change active to true if myArray is exact the same that one of the forArrays variants.

How can I do that? Should I keep forArrays an array as it is or should it be changed to an object to make this problem easier to solve?

So the only one of your examples that would pass is `myArray = ['4']`? — vol7ron, Mar 02 '18 at 21:26
@vol7ron yes - in this case, and first element will be activated — gileneusz, Mar 02 '18 at 21:29
@gileneusz will `myArray` ever have a comma-delimited set of numbers like your second object (e.g., `'2,3,4'`)? Or are you expecting `['2','3','4']` to match that case? — vol7ron, Mar 02 '18 at 21:31
If your `myArray = ['1','4']` will it match your second-to-last object? — vol7ron, Mar 02 '18 at 21:34
no, myArray elements could have only numbers 1-4 in this case, like "1", "2", "3", "4" — gileneusz, Mar 02 '18 at 21:35
@vol7ron arrays that could match second last object are only: myArray = ['1','4'] and myArray = ['2'] and myArray = ['4','1'] — gileneusz, Mar 02 '18 at 21:37

Nina Scholz · Answer 1 · 2018-03-02T22:06:06.817

1

You could iterate the objects and check if forArrays contains comma separated value.

For unsorted values, you could sort them in advanced.

function update(numbers) {
    function asc(a, b) { return a - b; }

    var values = numbers.slice().sort(asc).join();
    myObject.forEach(function (o) {
        if (o.forArrays.some(a => a.split(',').sort(asc).join() === values)) {
            o.active = true;
        }
    });
}

var myObject = [{ active: false, forArrays: ['2', '4'] }, { active: false, forArrays: ['2,3,4', '2,4'] }, { active: false, forArrays: ['2', '1,4'] }];

update(['1']);         // no change
console.log(myObject);

update(['2']);
update(['2', '4']);
console.log(myObject);

edited Mar 02 '18 at 22:06

answered Mar 02 '18 at 21:29

Nina Scholz

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Thank you for your answer, seems ok, but I cannot assume the same order... That is why I consider to change forArrays values to separate objects/arrays... – gileneusz Mar 02 '18 at 21:31
sorry for not responding to your edit, I was quite tired yesterday I and focused on vol7ron answer first. I see your answer is also correct and could be used to solve my problem. Thanks for posting it! – gileneusz Mar 03 '18 at 09:23

vol7ron · Accepted Answer · 2018-03-02T22:13:52.870

1

Given your comments, you can sort and join by commas and compare to each forArray element:

let myArray = ['1','4']

let myObject = [
   {active: false, forArrays:['2','4']},
   {active: false, forArrays:['2,3,4','2,4']},
   {active: false, forArrays:['2','1,4']},
   {active: false, forArrays:['2']},
]

let myArrayString = myArray.sort().join(',');

myObject.forEach( obj => 
  obj.active = obj.forArrays.some( el => 
    myArrayString === el.split(',').sort().join(',') 
  ) 
)

console.log(myObject);

edited Mar 02 '18 at 22:13

answered Mar 02 '18 at 21:38

vol7ron

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thank you for this solution, I will check it now – gileneusz Mar 02 '18 at 21:40
I'm trying to understand what this part of code is doing(?): `val=>{ val = val.split(',').sort().join(',')` – gileneusz Mar 02 '18 at 21:48
1

@gileneusz `val` is the element of your `forArray`. So `'4,2,1,3'` will become `'1,2,3,4'`, making string comparison more accurate – vol7ron Mar 02 '18 at 21:52
@gileneusz updated using `some` and always setting the active — see if that makes more sense for you – vol7ron Mar 02 '18 at 22:04
I'm trying to understand your code – gileneusz Mar 02 '18 at 22:10
There's only 3 lines ^_^ – vol7ron Mar 02 '18 at 22:12
started to learn full stack 4 months ago ;) and started coding today 14 hours ago ;) – gileneusz Mar 02 '18 at 22:13
1

First split string: `'2,4,3'.split(',')` => `['2','4','3']` Then sort values: `['2','4','3'].sort()` => `['2','3','4']` Then rebuild string: `['2','3','4'].join(',')` => `'2,3,4'` – vol7ron Mar 02 '18 at 22:16
1

That's all done because `myArray.sort().join(',');` so in the example `['1','4']` will become `'1,4'`. We can trust that the value we're checking and comparing to will always be in sorted order so an exact match can be done with string comparison – vol7ron Mar 02 '18 at 22:17
`obj =>` not `obj => {`? – gileneusz Mar 02 '18 at 22:19
a block (curly brace container) is only necessary when there's more than one statement. Otherwise it will be the return value of the arrow function – vol7ron Mar 02 '18 at 22:24
at this moment not working :) I need sleep – gileneusz Mar 02 '18 at 22:24
The example clearly works. – vol7ron Mar 02 '18 at 22:25
I do not doubt about it :) – gileneusz Mar 02 '18 at 22:27
I just prefer spaghetti code, It's more clean and readable – gileneusz Mar 02 '18 at 22:29
Ahh I guess readability improves with familiarity – vol7ron Mar 02 '18 at 22:33
It works! the only thing I've changed was: `myObject[i].active = obj.forArrays.some( el => ...` because I was in right Object already thanks to for loop. Thank you for help! – gileneusz Mar 02 '18 at 22:38
oh wait: `myObject[i].active = myObject[i].forArrays.some( el => ...` – gileneusz Mar 02 '18 at 22:44

javascript - comparing arrays elements

2 Answers2