ranges-offset^1.0.2

Increment or decrement each index in every range

Install via npm

npm i ranges-offset

The default is exported, so instead of offset below, you can name the consumed function however you want.

Consume via a require():

const offset = require("ranges-offset");

or as an ES Module:

import offset from "ranges-offset";

Install as a script, via CDN

Put this in your HTML:

<script src="https://cdn.jsdelivr.net/npm/ranges-offset/dist/ranges-offset.umd.js">

Then, you’ll get a global variable rangesOffset in your Global object and you consume it like this:

const offset = rangesOffset;

This offset is your main function. See its API in the main section.

Learn more about Ranges

We have a dedicated page about Ranges. Learn more

Trivia

This program has 23 assertions in its unit tests. That's less than all unit test assertions' median (51.5) and less than geometric mean (73).

§ Quick Take

import { strict as assert } from "assert";
import offset from "ranges-offset";

assert.deepEqual(
  offset(
    [
      [3, 5],
      [8, 7],
    ],
    10
  ),
  [
    [13, 15],
    [18, 17],
  ]
);

// ranges are empty, nothing happens:
assert.deepEqual(offset(null, 10), null);

// if input does not resemble ranges, nothing happens:
assert.deepEqual(offset(true, 10), true);

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§ API

offset(arr, offset)

Input argument	Type	Obligatory?	Description
`arr`	null or Array of one or more arrays	no	Provide an array of ranges to invert. Ranges do not have to be sorted or merged.
`offset`	Integer number	no	This number will be added to each index of every range.

Output:

if not ranges were passed, array of one or more arrays, same input will be returned
ELSE, offset value will be added to each index of every range

Inputs are not mutated.

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§ Purpose

For example, when working on parsed tokens, we have a value, chunk of string, but we know it starts at index X, not at zero. When we return zero-based result, receiving parties need to increment every index by X. The catch is, empty Ranges are null so Array.prototype.map() can't be used. Hence this library.

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