JS: Quote String

Double Quote

Use double straight quote (U+22: QUOTATION MARK) to enclose string.

"my cat"

Use \" for double quote in a double quoted string.

// deno-fmt-ignore
console.log("my \"3\" cat" === `my "3" cat`);

Single Quote

Single Quote (U+27: APOSTROPHE) can also be used.

Use \' for single quote in a single quoted string.

// single quoted string

// deno-fmt-ignore
console.log('my cat');
// my cat

// deno-fmt-ignore
// with escape
console.log('john\'s cat');
// john's cat

Difference Between Double and Single Quoted String

There's basically no difference, except that if you need to include a double/single quote, you need to escape it if it's the same delimiter.

Literal newline in double/single quoted string not allowed

Literal newline in double/single quoted string is not allowed. Use backslash to continue a line.

illegal syntax. Literal newline is not allowed

let xx = "a
b";

error: The module's source code could not be parsed

Characters Not Allowed in Double Quoted or Single Quoted String Literal

The following are not allowed in double quoted or single quoted string literal.

• U+005C REVERSE SOLIDUS (aka backslash)
• U+000D CARRIAGE RETURN (aka line return)
• U+2028 LINE SEPARATOR
• U+2029 PARAGRAPH SEPARATOR
• U+000A LINE FEED. (aka newline, line return)

If you include them without escape, you get syntax error.

"a
b"

SyntaxError: Invalid or unexpected token

to include these characters, use String Escape Sequence, or Template String .

Use Backslash to Continue a Line

let xx = "c\
d";

console.log(xx === "cd");

String Escape Sequence

Use \n for newline.

console.log("cat\ndog");
/*
prints
cat
dog
*/

[see String Escape Sequence]