How can i limit array size in type script?

Question

const arrPassword = []
const passarrayLength = 5


function addPassword(passwd) {
  if(arrPassword.length === passarrayLength)
  {
    arrPassword.shift()
  }

  arrPassword.push(passwd)
  console.log(arrPassword.length)
  console.log(arrPassword)
}

addPassword('Pass')
addPassword('Pass2')
addPassword('Pass3')
addPassword('Pass4')
addPassword('Pass5')
addPassword('Pass6')
addPassword('Pass7')
addPassword('Pass8')
addPassword('Pass9')
addPassword('Pass10')

I have a few cases where I want to store objects like user password history in an Array of objects to ensure he has not used the password in the last 5 times for example. My question is can I specify an array of objects with a size of 5 and then just push new passwords to array and any object in the array above size set would be discarded ? Or do I have to do this my self where I count the objects in my Array and if it is = max size I pop the oldest one before I push the new object to array ? Based on the research I did typescript or javascript does not have a fixed array size, I can specify a array of 3 5 objects but will need to assign all 5 and even so the push would make it 6 objects as there is no limit. So what would be the best approach to handle this ?

I included some basic concept i cam up with

Alex Wayne · Accepted Answer · 2021-04-16 18:46:32Z

2

Can I specify an array of objects with a size of 5 and then just push new passwords to array and any object in the array above size set would be discarded?

Nope. Arrays in javascript do not have a maximum size, so there is no "built in" way to do this.

Or do I have to do this my self where I count the objects in my Array and if it is = max size I pop the oldest one before I push the new object to array?

Yep, that's exactly right. It shouldn't be too hard to make a little class that handles this logic.

answered Apr 16, 2021 at 18:46

Alex Wayne

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Comments

Redu · Accepted Answer · 2021-04-17 19:05:04Z

1

When i need a functionality and there happens to be no such a functionality, the first thing that i think is "what am i missing?".

In this particular case all you need to do is to take the last passarrayLength many items from your arrPassword array and reassign it to the arrPassword array like;

arrPassword = arrPassword.slice(-passarrayLength);

like

[1,2,3].slice(-5);             // <- [1,2,3]
[1,2,3,4,5,6,7,8,9].slice(-5); // <- [5,6,7,8,9]

answered Apr 17, 2021 at 19:05

Redu

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3 Comments

ALP Over a year ago

You miss the point, the question was if something like that exists. So a slice(-X) would mean it will always limit the array to x no matter what the length is ? I wrote a function which checks before push the length and then slices 1 if its 20. slice(-X) seems to be a cleaner way if there is no drawbacks

Redu Over a year ago

@ALP The problem is... You can not have such a generic functionality because it can not tell from where you insert the new item and what you want to do accordingly. i.e.you can use .unshift(), .splice(), .push() or even a[a.length] = x to insert a new element. It's very undeterministic so the implementation of such a functionality is left to the programmer. In this particular case it seems logical to .push() a new item to your array whenever it happens and apply a .slice(-n) everytime before you need the resulting array.

ALP Over a year ago

Thanks for explanation

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