JavaScript Multiline Strings: Template Literals Guide

JavaScript multiline string literals can be assigned to variables using template literals (backticks), which were introduced in ES6. Template literals provide a clean syntax for multiline strings similar to Ruby’s heredoc, supporting both multiline content and variable interpolation.

Contents

• Template Literals: The Modern Approach
• Alternative Methods for Multiline Strings
• Comparison with Ruby Heredoc
• Best Practices and Browser Support
• Advanced Techniques and Libraries

Template Literals: The Modern Approach

Template literals, introduced in ES6, are the most elegant way to create multiline strings in JavaScript. They use backticks (`) instead of single or double quotes and can span multiple lines naturally.

Basic syntax:

let multilineString = `This
Is
A
Multiline
String`;

Variable interpolation (similar to Ruby’s heredoc):

let name = "JavaScript";
let version = "ES6";
let info = `This is ${name} version ${version}.
It supports multiline strings and variable interpolation.`;

Template literals preserve the exact formatting including newlines and indentation, making them perfect for creating code templates, HTML snippets, or any multi-line text content.

Key advantage: As CSS-Tricks explains, template literals provide a “simple way to print multiline strings in JavaScript” with built-in variable interpolation support.

Alternative Methods for Multiline Strings

While template literals are the preferred modern approach, there are other methods to achieve multiline strings in JavaScript:

1. String Concatenation with + Operator

let multilineString = "This" +
                      "Is" +
                      "A" +
                      "Multiline" +
                      "String";

Pros:

• Works in all JavaScript environments
• No special syntax required

Cons:

• Less readable
• Requires explicit line breaks
• Doesn’t preserve whitespace formatting

2. Using Escape Sequences

let multilineString = "This\nIs\nA\nMultiline\nString";

Pros:

• Universal compatibility
• Explicit control over line breaks

Cons:

• Manual management of each line break
• Less readable for complex multiline content

3. Backslash Continuation (Not Recommended)

let multilineString = "This \
Is \
A \
Multiline \
String";

Note: As mentioned in the CSS-Tricks article, this syntax “doesn’t seem to be a good practice and it’s not part of ECMAScript” despite working in some implementations.

Comparison with Ruby Heredoc

JavaScript doesn’t have a direct equivalent to Ruby’s heredoc syntax, but template literals provide similar functionality:

Ruby heredoc:

text = <<HERE
This
Is
A
Multiline
String
HERE

JavaScript template literal equivalent:

let text = `This
Is
A
Multiline
String`;

Key differences:

1. Syntax: Ruby uses <<IDENTIFIER while JavaScript uses backticks
2. Termination: Ruby requires an identifier on its own line, JavaScript uses closing backtick
3. Interpolation: Both support variable interpolation, but Ruby uses #{} while JavaScript uses ${}

Variable interpolation comparison:

• Ruby: "Hello #{name}"
• JavaScript: `Hello ${name}`

As Mozilla Developer Network explains, template literals “Any newline characters inserted in the source are part of the template literal,” making them functionally similar to heredocs.

Best Practices and Browser Support

Browser Compatibility

Template literals are supported in all modern browsers:

• Chrome 41+ (2015)
• Firefox 34+ (2014)
• Safari 9+ (2015)
• Edge 12+ (2015)

For older browsers, consider using transpilers like Babel or polyfills.

Best Practices

1. Use template literals for new code - They provide the cleanest syntax and best readability

2. Preserve indentation - Template literals maintain exact formatting, which is useful for templates:

const htmlTemplate = `
  <div class="container">
    <h1>Title</h1>
    <p>Content goes here</p>
  </div>
`;

3. Combine with string methods - Use .trim() to remove unwanted whitespace:

const cleanTemplate = `
  Some text
`.trim();

4. Use tagged templates for advanced formatting:

function html(strings, ...values) {
  return strings.reduce((result, string, i) => 
    result + string + (values[i] || ''), '');
}

const name = "World";
const output = html`<h1>Hello ${name}</h1>`;

Advanced Techniques and Libraries

1. Heredoc Emulation Libraries

If you prefer Ruby-like syntax, consider libraries like heredocument:

const heredoc = require('heredoc');
const text = heredoc`
  This
  Is
  A
  Multiline
  String
`;

2. JSON.stringify for Code Generation

For generating code snippets, use combination techniques:

const code = `function example() {
  console.log("Hello World");
}`;

3. Building Dynamic Templates

Create reusable template builders:

function createTemplate(templateFn, ...values) {
  return templateFn(...values);
}

const result = createTemplate(
  (name, age) => `User: ${name}, Age: ${age}`,
  "John", 30
);

Sources

1. Stack Overflow - How can I assign a multiline string literal to a variable?
2. CSS-Tricks - Multiline String Variables in JavaScript
3. FreeCodeCamp - JavaScript Multiline String – How to Create Multi Line Strings in JS
4. MDN - Template literals (Template strings)
5. Tutorialspoint - JavaScript - Multiline Strings
6. CareerKarma - JavaScript: MultiLine Strings Using \n and Template Literals
7. Stack Overflow - Javascript heredoc
8. GitHub - heredocument

Conclusion

• Template literals are the modern standard for multiline strings in JavaScript, providing clean syntax similar to Ruby’s heredoc functionality
• Variable interpolation works seamlessly using ${} syntax inside backticks
• Browser support is excellent in modern environments, with transpiler options for legacy code
• Ruby heredoc equivalent uses backticks instead of <<IDENTIFIER syntax
• Best practice is to use template literals for new code, especially when readability and formatting matter
• Advanced use cases include tagged templates and dynamic template builders for complex scenarios

The JavaScript approach using template literals actually offers more flexibility than Ruby’s heredoc, with built-in support for expressions, method chaining, and advanced string operations while maintaining the same readability for multiline content.