CODEWITHSUNDEEP
javascriptimmutability
user3162553
user3162553

Reputation: 2859

Correct way to permanently alter a JavaScript string

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?

Upvotes: 3

Views: 755

Answers (3)

knives22
knives22

Reputation: 303

assign the variable to itself like

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

Upvotes: 0

harmic
harmic

Reputation: 30587

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.

Upvotes: 3

rjz
rjz

Reputation: 16510

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

string = string.toUpperCase()

Upvotes: 0

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