Looping M Query function through list which includes column names to split DateTime

[RHOU]

Hi, I need some help optimizing a function to iterate through a list of columns. 

Here is my function which takes a Table and a column and then splits the DateTime columns into a separate Date field and a separate Time field (rounded to minutes) and then removes the original DateTime column. This works well and I use it all the time.

(varTable as table, varCol as text) => let
  Source = varTable,
  #"Inserted date" = Table.AddColumn(Source, varCol & " Date", each DateTime.Date(Record.Field(_,varCol)), type nullable date),
  #"Inserted time" = Table.AddColumn(#"Inserted date", varCol & " Time", each DateTime.Time(DateTime.From(DateTime.ToText(Record.Field(_,varCol),"HH:mm"))), type nullable time),
  #"Remove DateTime Column" = Table.RemoveColumns(#"Inserted time", varCol)
in
  #"Remove DateTime Column"

I would like to further improve this to allow varCol to not include just one column but be a list of columns so that I can use this function and include 5 DateTime fields in a table at once. I started below, but the problem is I have no idea how to loop through the varCols list for the two steps to add the columns and continously change the table. 

Does anybody have a tip?  

(varTable as table, varCols as list) => let
  Source = varTable,
  
// what needs to happen here to loop this section for each value in the varCols list???

  #"Inserted date" = Table.AddColumn(Source, varCol & " Date", each DateTime.Date(Record.Field(_,varCol)), type nullable date),
  #"Inserted time" = Table.AddColumn(#"Inserted date", varCol & " Time", each DateTime.Time(DateTime.From(DateTime.ToText(Record.Field(_,varCol),"HH:mm"))), type nullable time),
  
// until here
  
  #"Remove DateTime Column" = Table.RemoveColumns(#"Inserted time", varCols)
in
  #"Remove DateTime Column"

[jennratten]

Hello - if you are just wanting to get the time portion (rounded to minutes) from a list of DateTime fields, this is how you can do it.

BEFORE

RESULT

SCRIPT

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WMtE3MtQ3MjAyUjA0sDKytDIwVXD0VdLBEDcFi8fGAgA=", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [DateTime1 = _t, DateTime2 = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"DateTime1", type datetime}, {"DateTime2", type datetime}}),
    varColumnNames = {"DateTime1", "DateTime2"},
    TransformValues = Table.TransformColumns(#"Changed Type", List.Zip( { varColumnNames, 
        List.Repeat( {each DateTime.ToText ( _, "HH:mm" )}, List.Count( varColumnNames ) ) } ) )
in
    TransformValues

[RHOU · Accepted solution]

I was able to figure it out. The secret key ingredient is List.Accumulate and building a separate inner function to iterate. 

Here the final result that works. 

(varTable as table, varCols as list) => let
  
  // first define the inner function to iterate later
   sepDateTime = (varTable as table, varCol as text) => let
      Source = varTable,
      #"Inserted date" = Table.AddColumn(Source, varCol & " Date", each DateTime.Date(Record.Field(_,varCol)), type nullable date),
      #"Inserted time" = Table.AddColumn(#"Inserted date", varCol & " Time", each DateTime.Time(DateTime.From(DateTime.ToText(Record.Field(_,varCol),"HH:mm"))), type nullable time)
   in
      #"Inserted time",
   // inner function end    
  
  
  AddDateAndTimeColumns = List.Accumulate(varCols, varTable, (state, current) => sepDateTime(state,current)),
  RemoveAllDateTime = Table.RemoveColumns(AddDateAndTimeColumns, varCols)
in
  RemoveAllDateTime