scale-to

A functional utility to rescale numbers in a list to part of the given total.

API

scaleTo

• total: number - The total to scale to.
• list: number[] - The list of numbers to scale to total.

import { scaleTo } from 'scale-to';

const numbers = [1, 2, 3, 4];

scaleTo(1, numbers);
// [0.1, 0.2, 0.3, 0.4]

scaleObjectTo

• total: number - The total to scale to.
• object: { [key: string]: number } - The object of numbers to scale to total.

Returns the object with the scaled values.

import { scaleObjectTo } from 'scale-to';

const numberMap = { a: 1, b: 2, c: 3, b: 4 }

scaleObjectTo(1, numberMap);
// { a: 0.1, b: 0.2, c: 0.3, d: 0.4 }

Notes

• JavaScript has some inaccuracies with floating point numbers, which can cause unexpected results

  As an example, the list from the scaleTo example can result in 0.1, 0.2, 0.30000000000000004, 0.4.

• total is placed before list to ensure 'grammatical correctness'. You can, in theory, setup a prototype overload on core classes to work around this - but that is purely on your own accord.

  Array.prototype.scaleTo = function(total) {
    return scaleTo(total, this);
  }

• There was a possibility to implement an extract parameter or option to extract the list of numbers from an object, but I decided against it to remain consistant with the rest of the package. Use of predicates works when the target is of a specific type that is handled throughout a package, not so much when multiple types are accepted.

  // theortically speaking, this is what would be done
  // but i wouldn't know how to set a property on an object... fetched from a predicate
  const entities = [
    { ratio: 1 },
    { ratio: 2 },
    { ratio: 3 },
    { ratio: 4 }
  ];
  // scaleTo(total, list, predicate): each(list.*.ratio) / total
  scaleTo(1, entities, entity => entity.ratio);