index.js

var assert = require('assert')

var safeExternalLink = /(noopener|noreferrer) (noopener|noreferrer)/
var protocolLink = /^[\w-_]+:/

module.exports = href

function href (cb, root) {
  assert.notEqual(typeof window, 'undefined', 'nanohref: expected window to exist')

  root = root || window.document

  assert.equal(typeof cb, 'function', 'nanohref: cb should be type function')
  assert.equal(typeof root, 'object', 'nanohref: root should be type object')

  window.addEventListener('click', function (e) {
    if ((e.button && e.button !== 0) ||
      e.ctrlKey || e.metaKey || e.altKey || e.shiftKey ||
      e.defaultPrevented) return

    var anchor = (function traverse (node) {
      if (!node || node === root) return
      if (node.localName !== 'a' || node.href === undefined) {
        return traverse(node.parentNode)
      }
      return node
    })(e.target)

    if (!anchor) return

    if (window.location.protocol !== anchor.protocol ||
        window.location.hostname !== anchor.hostname ||
        window.location.port !== anchor.port ||
      anchor.hasAttribute('data-nanohref-ignore') ||
      anchor.hasAttribute('download') ||
      (anchor.getAttribute('target') === '_blank' &&
        safeExternalLink.test(anchor.getAttribute('rel'))) ||
      protocolLink.test(anchor.getAttribute('href'))) return

    e.preventDefault()
    cb(anchor)
  })
}