AutoMate/src/helpers.js

/** Parse and print engineering notation */
const prefixMap = {
  1e-24: 'y',
  1e-21: 'z',
  1e-18: 'a',
  1e-15: 'f',
  1e-12: 'p',
  1e-9: 'n',
  1e-6: 'u',
  1e-3: 'm',
  1: '',
  1e3: 'k',
  1e6: 'M',
  1e9: 'G',
  1e12: 'T',
  1e15: 'P',
  1e18: 'E',
  1e21: 'Z',
  1e24: 'Y'
}
const REGEX_ENG = /^([+-])?\s*(\d*\.?\d+|\d+\.?\d*)?([yzafpnumkMGTPTEZY]|e[+-]?\d+)?$/

export function printEng (number) {
  const factor = Object.keys(prefixMap).find((key) => {
    const ratio = Math.abs(number / key)
    return (ratio >= 1) && (ratio < 1000)
  })
  if (typeof factor !== 'undefined') {
    return (number / factor).toFixed(3).replace(/0+$/, '') + prefixMap[factor]
  } else {
    const base = Math.floor(Math.floor(Math.log10(Math.abs(number)) / 3))
    const value = (number / Math.pow(10, 3 * base)).toFixed(3).replace(/0+$/, '')
    return `${value}e${(3 * base).toFixed()}`
  }
}

export function parseEng (string) {
  const match = string.match(REGEX_ENG)
  if (!match) {
    return null
  }
  let num = 0
  let sign = 1
  let exp = 0
  if (match[1] === '-') {
    sign = -1
  }
  num = parseFloat(match[2])
  if (match[3] && match[3].length > 1) {
    exp = parseInt(match[3].substring(1))
  } else if (match[3]) {
    exp = prefixMap[match[3]]
  }
  return sign * num * Math.pow(10, exp)
}