The .toFixed() method is a built-in JavaScript function that formats a number using fixed-point notation. It’s particularly useful when you need to control the number of decimal places in a number, especially for displaying currency values or when working with precise measurements.
The .toFixed() method is called on a number and takes one optional argument, which is the number of digits to appear after the decimal point. It returns a string representation of the number with the specified number of decimal places. Here’s a basic example of how .toFixed() works:
let num = 3.14159;
console.log(num.toFixed(2)); // Output: "3.14"In this case, we’re limiting the number of decimal places to two. So, 3.14159 becomes 3.14. It’s important to note that .toFixed() returns a string, not a number. This is because the method is primarily intended for formatting numbers for display, not for further calculations.
The .toFixed() method rounds the number to the nearest value that can be represented with the specified number of decimal places. This rounding behavior is important to understand:
console.log((3.14159).toFixed(3)); // Output: "3.142"
console.log((3.14449).toFixed(3)); // Output: "3.144"
console.log((3.14550).toFixed(3)); // Output: "3.146"As you can see, .toFixed() rounds up when the next digit is 5 or greater, and rounds down otherwise. If you call .toFixed() without arguments, it defaults to 0 decimal places:
let num = 3.14159;
console.log(num.toFixed()); // Output: "3"The .toFixed() method can be particularly useful when working with financial calculations or displaying prices:
let price = 19.99;
let taxRate = 0.08;
let total = price + (price * taxRate);
console.log("Total: $" + total.toFixed(2)); // Output: "Total: $21.59"In this example, .toFixed(2) ensures that the total is always displayed with two decimal places, which is standard for currency in many countries.
In conclusion, the .toFixed() method is a powerful tool for formatting numbers in JavaScript, particularly when you need to control the display of decimal places. While it’s primarily used for formatting output, remember its behavior, especially when precise calculations are needed.