valid.js

// Validation function called by couch vdu
function validName (name) {
  if (!name) return false
  var n = name.replace(/^\s+|\s+$/g, '')
  if (!n || n.charAt(0) === "."
      || !n.match(/^[a-zA-Z0-9]/)
      || n.match(/[\/\(\)&\?#\|<>@:%\s\\\*'"!~`]/)
      || n.toLowerCase() === "node_modules"
      || n !== encodeURIComponent(n)
      || n.toLowerCase() === "favicon.ico") {
    return false
  }
  return n
}

console.log(validName("foo=bar"))
console.log(validName("foo~bar"))

// normalize-package-data/lib/fixer.js:293
function ensureValidName (name, strict) {
  if (name.charAt(0) === "." ||
      name.match(/[\/@\s\+%:]/) ||
      name !== encodeURIComponent(name) ||
      (strict && name !== name.toLowerCase()) ||
      name.toLowerCase() === "node_modules" ||
      name.toLowerCase() === "favicon.ico") {
        return new Error("Invalid name: " + JSON.stringify(name))
  }
  return name
}

console.log(ensureValidName("foo=bar"))
console.log(ensureValidName("foo~bar"))