In JavaScript, you can use quotes to define strings, either hard-coded strings in the program code or strings processed from user input. You can use single quotes or double quotes to achieve this, and recently, you have template literals. The latter can trip you off on the first time of usage. Nonetheless, this article is here to ensure that you know when and how to use quotes in JavaScript and some common pitfalls that you need to avoid.

Single Quotes vs. Double Quotes in JavaScript

The difference between single quotes and double quotes in JavaScript is the characters that represent them. For single quotes it is 'string' and for double quotes, it is "string". Both are valid for defining strings in JavaScript and in most cases they work similarly.

The following are code examples that show how to use single and double quotes in JavaScript:

let single_quoted = 'Hello, World!';
let double_quoted = "Hello, World!";

When to Use Single or Double Quotes

This boils down to preference, but it pays to be consistent in your code base. So, if you're going to use single quotes, use them all through. The same applies if you opt for double quotes. Irrespective of your choice, remember when a string contains single or double quotes, use the other to avoid escaping.

For example:

let sentence = "It's a wonderful day!";
let quote = 'He said, "Hello!"';

From the code above, the sentence variable contains a string that has single quotes, so it's best to enclose it using double quotes to prevent a syntax error. Meanwhile, the quote contains a string with double quotes, so we use single quotes to enclose the entire string to prevent a syntax error.

Handling Nested Quotes and Escape Characters

Nested quotes, if not handled properly, can lead to syntax errors (more on this later). To handle this, you can escape quotes using the backslash \ character. However, too much of this can cause readability issues.

For example, in the following code, the entire string is enclosed using single quotes. Meanwhile, the string contains another single quote that we escape using the backslash character.

let escaped = 'She said, "It\'s a wonderful world!"';
console.log(escaped);

Common Pitfalls and Debugging Tips

Most modern code editors should highlight when you have mismatched quotes in your code, helping you catch the error before you run your code. Nonetheless, I have an experience to share with you.

Once upon a time, I was using an SEO tool that taught me the importance of using the right quotes given the way the application works. This SEO tool in question shows keywords that it will recommend that you use in the article, and you can delete the ones that you don't want.

However, if the keyword contains single quotes, you can't delete it. I was amazed at this so I opened the Developer Tools, and I discovered that the function that was handling the deletion of the keywords was accepting those keywords in single quotes.

For example, delete_keywords('incoming keyword'). As a result, when incoming keyword contains a single quote, the function will become delete_keywords('incoming' keyword'), which leads to a syntax error. If the developer of the tool had anticipated this, they would have used double quotes to enclose the incoming keyword.

Template Literals: A Modern Alternative

Template literals in JavaScript are denoted with backticks. They are often preferred for complex or strings and you can use them to embed variables without concatenation. For the latter, you'll need to wrap it in a dollar sign and curly braces.

For example:

let name = "Alice";
let greeting = `Hello, ${name}! Welcome to JavaScript.`;
console.log(greeting);

Conclusion

Irrespective of the quotes that you choose to use, be consistent. If you need to escape a quote using the backslash character, don't overdo it. Finally, if you want to handle complex strings, you can use the template literals.