Since isNumber currently only checks if the value is a number or infinity.

function px (value: number | string) {
  if (G.isNumber(value)) return `${value}px`
  return px
}

px(1/0) // "Infinitypx"

// Proposal:
G.isFinite(1/0) // false

To be clear this does not actually add a new type guard since infinity is a number in javascript and typescript does not make the distinction.