How to Extract a Number Without a 'Tail' Using charCode in JavaScript

Learn how to avoid unwanted decimal tails when extracting numbers from strings in JavaScript, using character codes instead of native methods.
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How to Extract a Number Without a "Tail" Using charCode in JavaScript

In the world of programming, we often need to extract numbers from strings. However, sometimes the resulting numbers can have unwanted decimal tails due to floating-point arithmetic. This can be particularly cumbersome in languages like JavaScript, where precision issues may lead to unexpected outcomes. In this guide, we'll explore a solution for getting a clean numeric output from a given string using charCode.

The Problem

Imagine you have a multi-purpose string that includes numbers mixed with text, such as:

"Today I spent 56,02 USD, it's a lot for me."

When we try to extract the numeric value, we often end up with something like:

56.019999999999996

This unexpected output is due to the way floating-point numbers are represented in JavaScript. The goal is to extract the number 56,02 correctly.

Solution Overview

To solve this issue, we will:

Collect the integer and fractional parts separately.

Use charCode to build the number without relying on native parsing methods.

Avoid decimal precision issues by handling the parts distinctly.

Let’s take a look at the code to clarify how to implement this solution effectively.

The Code Implementation

Here is an example of how to extract a number without the trailing decimals using charCode:

[[See Video to Reveal this Text or Code Snippet]]

Explanation of the Code

We initialize several constants and variables:

zero, nine, and comma hold the character codes for 0, 9, and , respectively.

num, factor, and frac keep track of the number being formed and its parts.

We iterate over the string in reverse to handle the number formatting correctly.

As we encounter digits:

We build the integer part using num and update the factor accordingly.

When we reach a comma:

We save the fractional part separately, reset the main number (num), and allow the factor to represent the decimal place.

Finally, we return the combined result of the integer and fractional parts.

Conclusion

By using character codes instead of native methods, you can extract numbers from strings cleanly, avoiding the "tails" that can lead to confusion. This method not only maintains precision but also provides a clearer understanding of how values are derived from text.

If you ever find yourself needing to parse strings for numbers in JavaScript without the usual methods, this technique is certainly worth employing.