code: function hasPrecedence(op1, op2) {
      (0, _invariant2['default'])(PRECEDENCE[op1] && PRECEDENCE[op2], 'Missing precedence number for\n            ' + 
      JSON.stringify(op1) + ' or ' + JSON.stringify(op2) + '.\n            See ' + 
      JSON.stringify(PRECEDENCE));
  
      return PRECEDENCE[op1] < PRECEDENCE[op2];}
docs: Return true if the first operator has precedence over the second
  hasPrecedence('/', '+') => true
  
  @param {String} op1
  @param {String} op2