Template strings

Summary

Template strings are string literals allowing embedded expressions. You can use multi-line strings and string interpolation features with them.

Syntax

`string text`

`string text line 1
 string text line 2`

`string text ${expression} string text`

tag `string text ${expression} string text`

Description

Template strings are enclosed by the back-tick (` `) (grave accent) character instead of double or single quotes. Template strings can contain place holders. These are indicated by the Dollar sign and curly braces (${expression}). The expressions in the place holders and the text between them get passed to a function. The default function just concatenates the parts into a single string. If there is an expression preceding the template string (tag here),  the template string is called "tagged template string". In that case, the tag expression (usually a function) gets called with the processed template string, which you can then manipulate before outputting.

Multi-line strings

Any new line characters inserted in the source are part of the template string. Using normal strings, you would have to use the following syntax in order to get multi-line strings:

console.log("string text line 1\n\
string text line 2");
// "string text line 1"
// "string text line 2"

To get the same effect with multi-line strings, you can now write:

console.log(`string text line 1
string text line 2`);
// "string text line 1
//  string text line 2"

Expression interpolation

In order to embed expressions within strings, you had to use the following syntax:

var a = 5;
var b = 10;
console.log("Fifteen is " + (a + b) + " and not " + (2 * a + b) + ".");
// "Fifteen is 15 and not 20."

Now, with template strings, you are able to make use of the syntactic sugar making substitutions like this more readable:

var a = 5;
var b = 10;
console.log(`Fifteen is ${a + b} and not ${2 * a + b}.`);
// "Fifteen is 15 and not 20."

Tagged template strings

A more advanced form of template strings are tagged template strings. With them you are able to modify the output of template strings using a function. The first argument contains an array of string literals ("Hello " and " world" in this example). The second, and each argument after the first one, are the values of the processed (or sometimes called cooked) substitution expressions ("15" and "50" here). In the end, your function returns your manipulated string.

var a = 5;
var b = 10;

function tag(strings, ...values) {
  console.log(strings[0]); // "Hello "
  console.log(strings[1]); // " world"
  console.log(values[0]);  // 15
  console.log(values[1]);  // 50

  return "Bazinga!";
}

tag`Hello ${ a + b } world ${ a * b}`;
// "Bazinga!"

Raw strings

The special raw property, available on the first function argument of tagged template strings, allows you to access the raw strings as they were entered.

function tag(strings, ...values) {
  return strings.raw[0];
}

tag`string text line 1 \n string text line 2`;
// "string text line 1 \\n string text line 2"

In addition, the String.raw() method exists to create raw strings just like the default template function and string concatenation would create.

String.raw`Hi\n${2+3}!`; // "Hi\\n5!"

Specifications

Browser compatibility

See also

• String
• String.raw()
• Lexical grammar