indicating strings in javascript without quotation marks

Question

I came across a bit of code that looks something like this:

var str="I like blue";
str.replace(/blue/,"red");

What is happening here? When are string literals not required to be enclosed in quotes? What is the benefit of this approach as opposed to

str.replace("blue","red");

When it's a regular expression. [You can see from the docs](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/replace) that `String.replace` can take a regex as the first argument. — Andy, Jun 25 '14 at 15:35
The expression `/blue/` is a [regular expression literal](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions). — Pointy, Jun 25 '14 at 15:36
`/blue/` is not a string literal, it's a regular expression literal. `.replace` can search for either a string or a regex. — gen_Eric, Jun 25 '14 at 15:36
*"When are string literals not required to be enclosed in quotes?"* Never. *"What is the benefit of this approach as opposed to"* There is none in your example, but see http://stackoverflow.com/q/1144783/218196 — Felix Kling, Jun 25 '14 at 15:39
replace can do more things with regular expressions, you can replace patterns and also do global replaces, eg "abcbabcba".replace(/b/g,"_") // == "a_c_a_c_a" — imma, Jun 25 '14 at 15:40

score 1 · Answer 1 · answered Jun 25 '14 at 15:40

1

In Javascript, a literal enclosed within / characters is not a String, is a RegExp (regular expression)

So /blue/ is equivalent to new RegExp("blue")

answered Jun 25 '14 at 15:40

Pablo Lozano

score 1 · Accepted Answer · edited May 23 '17 at 12:11

When are string literals not required to be enclosed in quotes?

StringLiteral ::
    " DoubleStringCharacters_opt "
    ' SingleStringCharacters_opt '

(Note: template literals in ES6 are not string literals either.)

What is the benefit of this approach as opposed to [...]

There is none in your example, but if you want to replace all occurrences of a string, you have to use a regular expression with the global modifier: How to replace all occurrences of a string in JavaScript?

2 Answers2