Staaarter Tools

Integer Filter

Filters a list of integers down to only the values matching a selected mode (even, odd, positive, negative, or a custom min/max range), preserving the original order and outputting an empty result rather than an error when nothing matches. A free online tool from Staaarter, right in your browser.

Runs locallyUpdated 2026-07-27
integerfilterlist

Overview

Introduction

Filtering is one of the most common things you do with a list of numbers: keep only the even ones, only the positives, or only the ones inside a certain range.

This tool bundles the most common integer filter predicates into one place, so you can pick a mode and get back just the matching subset of your list, in order.

What Is Integer Filter?

A conditional list-selection tool: given a list of integers and a mode, it keeps only the values matching that mode and drops everything else.

The five supported modes cover parity (even/odd), sign (positive/negative), and a custom inclusive numeric range.

How Integer Filter Works

The list is parsed one integer per line, with blank lines skipped and invalid lines rejected before filtering runs.

Depending on the selected mode, each value is tested against the matching predicate: `value % 2 === 0` for even, `value > 0` for positive, `value >= min && value <= max` for in-range, and so on.

Values passing the predicate are kept in their original order and joined one per line; if none pass, the result is simply an empty string.

When To Use Integer Filter

Use it to quickly split a mixed list into just the values you care about before further processing.

It's useful for validating a dataset, e.g. confirming that a batch of IDs are all positive, or isolating outliers outside an expected range using the complementary tools.

Often used alongside Integer Clamper and Integer Pattern Finder.

Features

Advantages

  • Covers five of the most commonly needed integer filters in a single tool with one mode toggle.
  • Never treats "no matches" as an error, so it's safe to use for validation checks on unpredictable data.

Limitations

  • Only one filter mode applies per run; combining multiple conditions (e.g. even AND positive) requires running the tool twice.
  • The "in range" mode requires Min <= Max and rejects an inverted range as an error.

Examples

Filtering for even values

Input

1
2
3
4
-6

Output

2
4
-6

With mode=even, the odd values 1 and 3 are dropped, leaving 2, 4, and -6 (negative even numbers still count as even) in their original order.

Filtering in a custom range

Input

-5
0
10
25

Output

0
10

With mode="in range" and Min=0, Max=15: -5 is below the range and 25 is above it, leaving 0 and 10.

Best Practices & Notes

Best Practices

  • Use the "in range" mode's Min/Max as an inclusive bound; a value exactly equal to Min or Max is kept.
  • Chain this with Integer Clamper if you'd rather adjust out-of-range values than discard them.

Developer Notes

Filtering is implemented as a single `Array.prototype.filter` call with the predicate chosen by a `switch` on the mode string, keeping the parsing, validation, and selection logic clearly separated.

Integer Filter Use Cases

  • Splitting a mixed list of numbers into even/odd subsets for separate processing
  • Validating that a batch of values are all positive (or all within an expected range) before further use
  • Isolating outliers or in-range values from a raw data dump for analysis

Common Mistakes

  • Forgetting to set Min and Max when using "in range" mode, which the tool rejects as an error since there's nothing to compare against.
  • Expecting negative even numbers to be excluded from the "even" mode — parity, not sign, determines evenness.

Tips

  • Run the filter twice with complementary modes (e.g. positive, then negative) to quickly split a list into two halves.
  • Use "in range" with Min and Max set to the same value to filter for one exact number across a large list.

References

Frequently Asked Questions