JavaScript Equivalent of Python f-String

Python f-strings allows us to embed expressions inside string literals, making the code more readable and concise. However, JavaScript doesn’t have a built-in f-string feature like Python, but it provides a variety of ways to achieve similar functionality. In this article, we will explore how to replicate the behavior of Python f-strings in JavaScript.

What are Python f-strings?

In Python, f-strings (formatted string literals) were introduced in Python 3.6 as a way to embed expressions inside string literals. The syntax is simple: the string is prefixed with the letter f and variables or expressions can be embedded within curly braces {}.

Example of Python f-strings:

n = "Shivang"
age = 22
s = f"My name is {n} and I am {age} years old."
print(s)

My name is Shivang and I am 22 years old.

As seen in the example, f-strings make it easy to embed variables and expressions directly into strings without needing concatenation or format methods.

Template Literals (Backticks)

The closest and most common JavaScript equivalent to Python f-strings are template literals, which allow embedding expressions within strings using ${}.

Example of JavaScript Template Literals:

const n = "Shivang";
const age = 22;
const s = `My name is ${n} and I am ${age} years old.`;
console.log(s);

My name is Shivang and I am 22 years old.

Explanation:

• Template literals are wrapped in backticks (`) rather than quotes (' or ") and can include placeholders ${} where expressions or variables are evaluated and embedded directly within the string.
• This approach works similarly to Python f-strings, making it the most direct equivalent in JavaScript.

While JavaScript doesn't support f-strings natively, there are several alternatives in JavaScript that offer similar functionality. Below are the main methods:

String Concatenation in JavaScript

Before template literals were introduced in JavaScript (in ES6), developers had to rely on string concatenation using the + operator. Although this method is still available, it’s less readable and convenient compared to template literals.

Example of String Concatenation in JavaScript:

const n = "Shivang";
const age = 22;
const s = "My name is " + n + " and I am " + age + " years old.";
console.log(s);

My name is Shivang and I am 22 years old.

Explanation:

• Here, we manually concatenate the strings using the + operator. It works well for combining values into a single string, but as the number of variables or expressions increases, the readability of the code decreases.
• This method is not as clean or readable as template literals or Python f-strings.

String concat() Method to Concatenate Strings

Another older way of concatenating strings is using JavaScript’s built-in concat() method. This approach is similar to string concatenation but makes use of a method rather than the + operator.

Example of concat() Method:

const n = "Shivang";
const age = 22;
const s = "My name is ".concat(n, " and I am ", age, " years old.");
console.log(s);

My name is Shivang and I am 22 years old.

Explanation:

• The concat() method joins multiple strings or variables together. However, like string concatenation, it can become cumbersome as the number of variables grows.
• This method is more verbose than template literals and doesn't offer the same readability or flexibility.

String.format() (Using External Libraries in NodeJS Environment)

In the absence of a native String.format() function in JavaScript (like in Python), some developers use external libraries such as sprintf-js or util.format() from Node.js to mimic the Python-style formatting.

Example of Using sprintf-js:

const sprintf = require("sprintf-js").sprintf;
const n = "Shivang";
const age = 22;
const s = sprintf("My name is %s and I am %d years old.", n, age);
console.log(s);

Output:

My name is Shivang and I am 22 years old.

Explanation:

• The sprintf-js library enables Python-like string formatting by using placeholders like %s for strings and %d for numbers. It’s a powerful and flexible solution, especially for more complex string formatting needs.
• This method is more commonly used in legacy systems or environments where external libraries are already being used.