Strings

In JavaScript, the textual data is stored as strings. There is no separate type for a single character.

The internal format for strings is always UTF-16, it is not tied to the page encoding.

Quotes

Let’s recall the kinds of quotes.

Strings can be enclosed within either single quotes, double quotes or backticks:

let single = 'single-quoted';
let double = "double-quoted";

let backticks = `backticks`;

Single and double quotes are essentially the same. Backticks, however, allow us to embed any expression into the string, by wrapping it in ${…}:

function sum(a, b) {
  return a + b;
}

alert(`1 + 2 = ${sum(1, 2)}.`); // 1 + 2 = 3.

Another advantage of using backticks is that they allow a string to span multiple lines:

let guestList = `Guests:
 * John
 * Pete
 * Mary
`;

alert(guestList); // a list of guests, multiple lines

Looks natural, right? But single or double quotes do not work this way.

If we use them and try to use multiple lines, there’ll be an error:

let guestList = "Guests: // Error: Unexpected token ILLEGAL
  * John";

Single and double quotes come from ancient times of language creation, when the need for multiline strings was not taken into account. Backticks appeared much later and thus are more versatile.

Backticks also allow us to specify a “template function” before the first backtick. The syntax is: func`string`. The function func is called automatically, receives the string and embedded expressions and can process them. This feature is called “tagged templates”, it’s rarely seen, but you can read about it in the MDN: Template literals.

Special characters

It is still possible to create multiline strings with single and double quotes by using a so-called “newline character”, written as \n, which denotes a line break:

let guestList = "Guests:\n * John\n * Pete\n * Mary";

alert(guestList); // a multiline list of guests, same as above

As a simpler example, these two lines are equal, just written differently:

let str1 = "Hello\nWorld"; // two lines using a "newline symbol"

// two lines using a normal newline and backticks
let str2 = `Hello
World`;

alert(str1 == str2); // true

There are other, less common special characters:

As you can see, all special characters start with a backslash character \. It is also called an “escape character”.

Because it’s so special, if we need to show an actual backslash \ within the string, we need to double it:

alert( `The backslash: \\` ); // The backslash: \

So-called “escaped” quotes \', \", \` are used to insert a quote into the same-quoted string.

For instance:

alert( 'I\'m the Walrus!' ); // I'm the Walrus!

As you can see, we have to prepend the inner quote by the backslash \', because otherwise it would indicate the string end.

Of course, only the quotes that are the same as the enclosing ones need to be escaped. So, as a more elegant solution, we could switch to double quotes or backticks instead: