Linear scale of a number between two ranges

The arrow-function form of the same mapping.

JavaScript Version 1.0.0 · MIT · .md

function scale({ value, from, to }) { return ((value - from[0]) * (to[1] - to[0])) / (from[1] - from[0]) + to[0]; }

Input & expected output

{
  "value": 0.5,
  "from": [
    0,
    1
  ],
  "to": [
    0,
    255
  ]
}

127.5

The edge case

{
  "value": 2,
  "from": [
    0,
    1
  ],
  "to": [
    0,
    10
  ]
}

20

Know the limits

• Values outside the input range extrapolate, as the edge case shows.

The function above is the implementation used by the lab. The lab validates JSON types and caps size before execution; include equivalent validation when accepting untrusted input in your application.

Keep exploring

• Convert degrees to radians — Multiply by π and divide by 180.
• Check if a rectangle contains another one — Compare corners: a contains b when b’s corners sit inside or on a’s edges.
• Check if a rectangle overlaps another one — Two rectangles overlap when they overlap on both axes.