What is parsefloat in javascript?

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The `parseFloat` function in JavaScript is used to convert a string into a floating-point number. It is a built-in function that is commonly used when dealing with user input or when working with numeric values in string format. This article will delve deeper into the functionality and usage of `parseFloat` in JavaScript.

Understanding parseFloat

The `parseFloat` function takes a string as its argument and attempts to parse it into a floating-point number. It starts reading the string from the beginning until it encounters a character that is not a valid part of a number. It then stops parsing and returns the number it has parsed so far.

It is important to note that `parseFloat` only parses the beginning of the string until it encounters an invalid character. This means that if the string contains any non-numeric characters after a valid number, they will be ignored. For example, `parseFloat(“10.5abc”)` will return `10.5`, ignoring the “abc” part.

Usage and Examples

The `parseFloat` function can be used in various scenarios, such as converting user input into a numeric value or extracting numbers from a string. Let’s explore some examples to understand its usage better:

Example 1: Converting user input into a number:
let userInput = prompt(“Enter a number:”);
let number = parseFloat(userInput);
In this example, the `parseFloat` function is used to convert the user’s input into a floating-point number. The parsed number is then logged to the console.

Example 2: Extracting numbers from a string:
let text = “The price is $10.99”;
let price = parseFloat(text.match(/d+.d+/));
Here, the `parseFloat` function is used in conjunction with a regular expression to extract the price value from the given string. The `match` method returns an array containing the matched number, which is then parsed using `parseFloat`.

Handling Edge Cases

When using `parseFloat`, it is essential to consider some edge cases that may affect the parsing behavior. For instance:

Leading and trailing whitespace: `parseFloat` ignores leading and trailing whitespace characters, but it stops parsing as soon as it encounters an invalid character. So, if there are non-numeric characters after the whitespace, they will be ignored.

Empty string: If the string passed to `parseFloat` is empty or contains only whitespace characters, it will return `NaN` (Not a Number).

Invalid number format: If the string does not start with a valid number representation, `parseFloat` will return `NaN`. For example, `parseFloat(“abc123”)` will return `NaN`.


In conclusion, the `parseFloat` function in JavaScript is a useful tool for parsing strings into floating-point numbers. It allows developers to convert user input or extract numeric values from strings easily. However, it is important to be aware of its limitations and handle edge cases appropriately to ensure accurate parsing.


– developer.mozilla.org
– www.w3schools.com