Parse query string in browser (<=ES5)

queryStringParse.js

// Deserialize query string to object
// Example: var queryParams = queryStringParse(window.location.search)
  function queryStringParse (str) {
    var ret = Object.create(null)

    if (typeof str !== 'string') {
      return ret
    }

    str = str.trim().replace(/^(\?|#|&)/, '')

    if (!str) {
      return ret
    }

    str.split('&').forEach(function (param) {
      var parts = param.replace(/\+/g, ' ').split('=')
      // Firefox (pre 40) decodes `%3D` to `=`
      // https://github.com/sindresorhus/query-string/pull/37
      var key = parts.shift()
      var val = parts.length > 0 ? parts.join('=') : undefined

      key = decodeURIComponent(key)

      // missing `=` should be `null`:
      // http://w3.org/TR/2012/WD-url-20120524/#collect-url-parameters
      val = val === undefined ? null : decodeURIComponent(val);

      if (ret[key] === undefined) {
        ret[key] = val
      } else if (Array.isArray(ret[key])) {
        ret[key].push(val)
      } else {
        ret[key] = [ret[key], val]
      }
    })

    return ret
  }