In JavaScript, working with numbers is a common task, whether you’re calculating values, formatting numbers for display, or converting strings to numeric values.

JavaScript provides several built-in methods and functions to help with these tasks. Understanding how to use toFixed(), toPrecision(), toString(), parseInt(), and parseFloat() is essential for effectively manipulating and converting numeric values.

Number Formatting Methods

I. toFixed()

The toFixed() method formats a number using fixed-point notation, meaning it shows a specified number of digits after the decimal point.

• Syntax: num.toFixed([digits])
• Example:

let number = 123.456;
console.log(number.toFixed(2)); // "123.46"

This method is useful for formatting currency or other precise decimal values.

II. toPrecision()

The toPrecision() method formats a number to a specified length. Unlike toFixed(), toPrecision() includes digits before and after the decimal point in its count.

• Syntax: num.toPrecision([precision])
• Example:

let number = 123.456;
console.log(number.toPrecision(5)); // "123.46"

This method is handy when you need a specific overall precision for a number, not just after the decimal point.

III. toString()

The toString() method converts a number to its string representation. Optionally, you can specify a radix (base) for the conversion.

• Syntax: num.toString([radix])
• Example:

let number = 10;
console.log(number.toString()); // "10"
console.log(number.toString(2)); // "1010" (binary representation)

This method is useful for converting numbers to strings for display or processing as text.

Converting Strings to Numbers

Sometimes you need to convert string representations of numbers back into numeric types. JavaScript provides two functions for this purpose: parseInt() and parseFloat().

I. parseInt()

parseInt() parses a string and returns an integer. It takes two arguments: the string to parse and an optional radix (base) for conversion.

• Syntax: parseInt(string, [radix])
• Example:

let stringNumber = "123.456";
console.log(parseInt(stringNumber)); // 123

This function is useful when you need to extract integer values from strings.

II. parseFloat()

parseFloat() parses a string and returns a floating-point number.

• Syntax: parseFloat(string)
• Example:

let stringNumber = "123.456";
console.log(parseFloat(stringNumber)); // 123.456

This function is essential for extracting floating-point numbers from strings, preserving decimal points.

Conclusion

Mastering the use of number methods and conversion functions in JavaScript is crucial for handling numeric data effectively. Whether you’re formatting numbers for display with toFixed() and toPrecision(), converting numbers to strings with toString(), or parsing strings into numbers with parseInt() and parseFloat(), these tools are indispensable for JavaScript developers.