Overview
Introduction
This tool takes a list of integers and highlights every occurrence of a single digit you choose, character by character, across the whole list.
It's a focused visual aid for spotting exactly where a specific digit shows up (or doesn't) across many values at once.
What Is Integer Digit Highlighter?
A per-character highlighting tool for lists of integers, one value per line, where every character of every value is rendered as its own span.
Only the digit characters matching your chosen "highlight digit" (0-9) get a visual highlight; every other digit, and the sign character on negative values, stays in the default text color.
How Integer Digit Highlighter Works
The list is parsed and validated first; every non-blank line must be a plain integer, or the tool reports which line failed.
Each value's characters are split individually, and every digit character is compared against the chosen highlight digit; the sign character (if present) is never compared or highlighted.
The component renders one span per character, styling only the matches, following the same per-character span pattern this site's hex digit colorizer uses.
When To Use Integer Digit Highlighter
Use it to visually audit a list of IDs, codes, or counters for how often a particular digit appears.
It's also useful as a teaching aid for digit frequency or place-value concepts, letting learners see a digit's occurrences highlighted directly in context.
Often used alongside Integer Highlighter, Integer Digit Colorizer and Integer Digit Picker.
Features
Advantages
- Highlights at the individual-character level, so you can see exactly which position(s) within a multi-digit value match, not just whether the value contains the digit somewhere.
- Leaves the sign character reliably unhighlighted, so negative numbers are never misread as containing an extra digit occurrence.
- Provides an unmodified plain-text copy of the list alongside the visual highlighting.
Limitations
- Only supports highlighting one digit (0-9) at a time; comparing multiple digits requires running the tool again with a different highlight digit.
- Purely visual: it doesn't count occurrences or produce a frequency summary, just highlights matches in place.
- Only understands plain decimal integers, one per line.
Examples
Best Practices & Notes
Best Practices
- Use this after generating or receiving a list of IDs to quickly spot which ones contain (or are free of) a specific digit.
- Combine with the Integer Digit Colorizer if you want every digit distinctly colored rather than just one digit highlighted.
Developer Notes
The lib returns a `lines: IntegerDigitSegment[][]` array (one array of `{char, highlighted}` segments per input line) so the component can render one span per character with a simple boolean-driven style, mirroring the hex category's per-character colorizer pattern but with a binary highlight flag instead of a rotating palette index.
Integer Digit Highlighter Use Cases
- Auditing a list of IDs or codes for how often a specific digit appears
- Teaching digit frequency or place-value concepts with highlighted examples
- Visually verifying the output of another tool (like a digit picker or fuzzer) at a glance
Common Mistakes
- Expecting the sign character to be highlightable; it's intentionally excluded from every comparison.
- Assuming the tool counts or summarizes digit occurrences; it only highlights them in place, it doesn't tally them.
- Forgetting the highlight digit must be a single whole number from 0 to 9; anything else is rejected.
Tips
- Try highlighting 0 first on a list of IDs to quickly spot values with unexpected leading or embedded zeros.
- Use the plain-text copy output when you just need the original list back without the visual formatting.