Similar to parse-boolean, to turn a string into a boolean, but it permits numbers, actual booleans, number-strings, and yes|no|true|false strings (case-insensitive, even with padding.)

parseBoolean.js

const isString = require('is-string')
const isNumber = require('is-number')

const parseBoolean = (string, defaultValue = null) => {
  // handle booleans & numbers
  if (!isString(string)) {
    return !!string
  }

  // handle numbers/number-strings
  if (isNumber(string)) {
    return !!parseFloat(string)
  }

  // handle strings
  switch (string.trim().toLowerCase()) {
    case 'true': return true
    case 'false': return false
    case 'yes': return true
    case 'no': return false
    default: return defaultValue
  }
}

module.exports = parseBoolean

// "true" = true
// "false" = false
// "True" = true
// "False" = false
// "TRUE" = true
// "FALSE" = false
// "yes" = true
// "no" = false
// "Yes" = true
// "No" = false
// "YES" = true
// "NO" = false
// true = true
// false = false
// 1 = true
// -1 = false
// 0 = false
// 2 = true
// "1" = true
// "-1" = false
// "0" = false
// "2" = true
// [] = true
// {} = true