Looping through JSON to generate a total based on similarly-named numeric fields [closed]

I’ve got a JSON data set like so:

 { "ts": "4", "FlowvolMeas_dL_12_hr": "3612.82", "FlowvolUnexp_dL_12_hr": "40.26" },
 { "ts": "5", "FlowvolMeas_dL_12_hr": "237.15",  "FlowvolUnexp_dL_12_hr": "0.98" },
 { "ts": "6", "FlowvolMeas_dL_12_hr": "12.04",   "FlowvolUnexp_dL_12_hr": "0.2" },

and another like so:

 { "ts": "4", "FlowvolMeas_dL_30_min": "12", "FlowvolUnexp_dL_12_hr": "2" },
 { "ts": "5", "FlowvolMeas_dL_30_min": "22", "FlowvolUnexp_dL_12_hr": "3" },
 { "ts": "6", "FlowvolMeas_dL_30_min": "33", "FlowvolUnexp_dL_12_hr": "4" }, ...

What I hoping to do is do a sort of global addition of two fields without needing to individually define each case, i.e. 30_min and 12_hr.

Some sort of loop I am thinking of that when I encounter anything with a prefix of FlowvolMeas and FlowvolUnexp, I add the two values together and append the total to the end of that same record.

Something like a wildcard search, perhaps? Whatever the JavaScript equivalent of total = FlowvolMeas* + FlowvolUnexp* would be, followed by appending that new key-value pair to the end of the record.