Скачать или смотреть How to Enforce Either $ or % in Your Input with Regex in Angular

Learn how to implement a regex solution in your Angular 9 application that allows only either `$` or `%` in user inputs, ensuring a seamless experience for entering numeric values.
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This video is based on the question https://stackoverflow.com/q/63906971/ asked by the user 'Laurence MacNeill' ( https://stackoverflow.com/u/2620218/ ) and on the answer https://stackoverflow.com/a/63911631/ provided by the user 'wp78de' ( https://stackoverflow.com/u/8291949/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Enforcing Either $ or % in Angular Input Fields Using Regex

When developing web applications, providing a user-friendly input experience is essential. A common scenario arises when you want users to enter a numeric value with a trailing currency sign ($) or a percentage sign (%). However, allowing both signs simultaneously can lead to confusion. In this post, we’ll tackle how you can restrict user input to ensure that only one of these characters can be entered at a time.

The Problem at Hand

In your Angular application, you have a text input field where users are supposed to type in an amount, potentially followed by either a dollar sign or a percentage sign. However, you want to prevent users from inputting both signs at once. Currently, your input field allows for numbers, a decimal point, and both signs, which is not ideal.

Current Implementation

Here’s a snippet of your current implementation:

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

This setup removes any character that is not a number, a dollar sign, a percentage sign, or a decimal point. However, it does not enforce the rule of having only one type of sign at any time.

Solution Breakdown

To refine your user input handling, we will utilize a regular expression (regex) that checks for the conditions you want to enforce. Here’s a structured approach to implement this solution.

Step 1: Understanding the Regex Pattern

We need a regex pattern that does the following:

Accepts numeric values including decimal points.

Allows either a % or $ sign, but not both.

Here’s the updated code snippet with the regex adjustment:

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

Explanation of the Regex:

^ – Start of the string.

((?:[0-9]+ .?[0-9]*)[%$]?) – This part captures the numeric value and an optional sign by using a non-capturing group:

[0-9]+ matches one or more digits,

.? optionally matches a decimal point,

[0-9]* matches zero or more digits after the decimal,

[%$]? makes either the % or $ sign optional.

.* – Matches the rest of the string and ignores it.

'$1' – Only retains the captured group with the valid input.

Step 2: Allowing for Further Specifications

If you want to limit the decimal precision or the order of the signs, you can modify the regex more specifically. Here’s an example if you want to allow a maximum of two decimal places:

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

Key Modifications:

(?:[0-9]*.?[0-9]{0,2}) limits to two decimal places.

The order of possible signs can be adjusted to fit your requirements.

Step 3: Testing the Implementation

Once you've adjusted your regex, it’s important to test the input field thoroughly. Try various combinations to ensure that:

Only numbers are allowed.

Only one sign can appear after the numeric value.

Invalid combinations are filtered out effectively.

Conclusion

By implementing this regex solution in your Angular application, you can greatly enhance the user input experience for numeric values with trailing currency or percentage signs. With clear enforcement of input rules, users are less likely to make errors, and your application can handle data inputs more smoothly.

If you have any further questions or require assistance with your Angular project, feel free to reach out! Happy coding!