The json Text parameter was not valid JSON

Question

I am using a!fromJson to convert a JSON string into an Appian value. However, I encounter an error when handling document types. 
 This is the current format I am using: 
 in ER: """" & fv!item & """:[" & substitute(if(rule!GLB_isBlank(local!data[fv!item]), "", local!data[fv!item]),";",",") & "]", OUTPUT: "fieldName":[[Document:115497], [Document:115501]] 
 but It's giving error 'The json Text parameter was not valid JSON'

Harshit Bumb (Appyzie) · Answer

Try to wrap your local!data[item] into integer. This will give you just the numbers and it will become an integer array. 
 """" & fv!item & """:[" & substitute(
 if(
 rule!GLB_isBlank(local!data[fv!item]),
 "",
 tointeger(local!data[fv!item])
 ),
 ";",
 ","
) & "]"