Correct way to permanently alter a JavaScript string

Question

In Ruby, if I want to modify a string and have it change the original string, I can use the ! bang character.

string = "hello"
string.capitalize!
> "Hello"
string
> "Hello"

In JavaScript, I can't find this equivalence. Modifying a string to be upperCase for instance returns the original string after the first instance.

var string = "hello";
string.toUpperCase();
> "HELLO"
string
> "hello"

I know I can save it as a variable such as

var upperCaseString = string.toUpperCase();

but this seems inefficient and is undesirable for my purposes.

I know it must be obvious, but what am I missing?

It seems string is immutable in javascript like java.

Panther
– Panther

2015-07-02 05:04:46 +00:00
Commented Jul 2, 2015 at 5:04 — Panther
– Panther, Commented Jul 2, 2015 at 5:04

harmic · Accepted Answer · 2015-07-02 05:05:24Z

3

The return value of the toUpperCase is a new string which is capitalized. If you want to keep that and throw away the original, use this:

string = string.toUpperCase();

BTW, when entering JS statements on the command line of node.js and similar environments, it prints the result of evaluating each expression, which is why you see the uppercase version if you just type

string.toUpperCase();

As you have deduced that has no effect on the original string.

answered Jul 2, 2015 at 5:05

harmic

31k6 gold badges75 silver badges102 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

user3162553 Over a year ago

Alright, that would explain why I had a tough time finding the equivalence. Thanks!

rjz · Accepted Answer · 2015-07-02 05:04:39Z

0

Strings in JavaScript pass exist as values, not references, so you've got it: reassignment.

string = string.toUpperCase()

answered Jul 2, 2015 at 5:04

rjz

16.5k3 gold badges39 silver badges35 bronze badges

Comments

knives22 · Accepted Answer · 2015-07-02 05:11:46Z

0

assign the variable to itself like

var string = "hello";
string = string.toUpperCase();

answered Jul 2, 2015 at 5:11

knives22

3031 gold badge2 silver badges14 bronze badges

Collectives™ on Stack Overflow

Correct way to permanently alter a JavaScript string

3 Answers 3

1 Comment

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

1 Comment

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related