seems to only cycle n times group? How to randomly select n items from a known array to form a new array? 
  
 
 seems to only cycle n times group? How to randomly select n items from a known array to form a new array? 
  
 
  
 
 Let a function return the desired array as a function 
  use @ shuffle  
 `Mock.mock ({
new_arr: '@shuffle([1, 2, 3, 4, 5], 2, 4)'}) `
the front end wants to simulate data through rap. How to set the API for adding, deleting, modifying and querying ...