index.js
function type (prop) {
  var rs = Object.prototype.toString.call(prop);
  return rs.slice(8, rs.length - 1).toLowerCase();
}
function type (prop) {
  var rs = Object.prototype.toString.call(prop);
  return rs.slice(8, rs.length - 1).toLowerCase();
}
function type ( prop ) { var rs = Object . prototype . toString . call ( prop ) ; return rs . slice ( 8 , rs . length - 1 ) . toLowerCase ( ) ; }
Strict type checking.

@param {Mixed} prop
@returns {String}
@api private
Strict type checking .