Passing arguments to another function and returning changed value does not working

Question

can some please explain why this function returns its original argument value instead of the altered value.

edit: FYI I know the solution to the problem already i just don't understand what is going on 'under the hood'; what is causing this not to work. i want better understanding of the language

function helper(value){
  let hold = value;
    hold.replace(/[^\w]/g, '')
    hold.split('')
    hold.sort()
    hold.join('')
    hold.toLowerCase()

    return hold
}

console.log(helper('hello world')) <--- returns 'hello world'

all functions written here, return value but won't change it unless it is assigned back to that variable. — Vivek, Jun 02 '18 at 15:12
Possible duplicate of [JS replace not working on string](https://stackoverflow.com/questions/12231644/js-replace-not-working-on-string) — Sebastian Simon, Jun 02 '18 at 15:24
Please try using the [debugging capabilities](https://developer.mozilla.org/en-US/docs/Mozilla/Debugging/Debugging_JavaScript) of your browser. Simply calling the method doesn’t mutate the variable, therefore you’re not returning a string with any modifications. The only exception is `sort` which sorts arrays in-place. But since you’re not storing any result anywhere, even that is lost. — Sebastian Simon, Jun 02 '18 at 15:27

Nikhil Aggarwal · Answer 1 · 2018-06-02T17:53:29.493

3

You need to reassign, the functions does not change the original value and needs to be re-assigned. You can also use dot operator to combine all the operations and shorten the code like following

function helper(value){
    return value.replace(/[^\w]/g, '').split('').sort().join('').toLowerCase();
}

console.log(helper('hello world'))

Alternatively, you can correct your code like this

function helper(value){
  let hold = value;
  hold = hold.replace(/[^\w]/g, ''); // re-assign
  hold = hold.split(''); // re-assign
  hold.sort(); // sort updates hold - re-assignment not required
  hold = hold.join(''); // re-assign
  hold = hold.toLowerCase(); // re-assign
  return hold;
}

console.log(helper('hello world'))

edited Jun 02 '18 at 17:53

answered Jun 02 '18 at 15:12

Nikhil Aggarwal

28,197
4
43
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1

Why's there a `.hold` after each operation? – Sid Jun 02 '18 at 15:14
@Sid - Not required. Corrected. Thanks! – Nikhil Aggarwal Jun 02 '18 at 15:15
@NikhilAggarwal “Not required” implies that it’s optional to remove `.hold`, but it’s not. – Sebastian Simon Jun 02 '18 at 15:28
@Xufox - Ohhh! I meant the **mandatory** not required. I think it is the different in the perception towards the statement. :) – Nikhil Aggarwal Jun 02 '18 at 15:35
i used the hold variable after using the argument value.. i thought that assigning the argument would fix the problem – mayo19 Jun 02 '18 at 16:46
i did reassign. that is the purpose of the hold variable – mayo19 Jun 02 '18 at 16:55
@mayo19 - I have updated my answer - hope it clarifies – Nikhil Aggarwal Jun 02 '18 at 17:57

score 1 · Answer 2 · answered Jun 02 '18 at 15:14

1

replace doesn't modify input argument but returns a new string instead.

answered Jun 02 '18 at 15:14

PeteH

79
6

score 0 · Accepted Answer · answered Jun 03 '18 at 08:17

I have found the solution as to "WHY" the code was acting the way it was. it is because Arrays and Objects are mutable, while strings and numbers and other primitives are immutable.

for more info read this blog What are immutable and mutable data structures?

and the solution was posted here by "Nikhil Aggarwal"

Passing arguments to another function and returning changed value does not working

3 Answers3