What is correct syntax to update SP multiperson column with array or string variable via rest api?

Can’t get the syntax right to update a SharePoint multiperson column.

some variables:

iArray // = array of multiple user ids sArray = iArray.join(); // string of multiple user ids json1 = "{'results': [" + iArray + "]}"; json2 = "{'results': [" + sArray + "]}"; 

hardcoding ids works:

data: JSON.stringify({ 'From_x0020_ContactsId': {'results': [9,25]}, '__metadata': { 'type': 'SP.Data.Lib_x005f_RFI2Item' } }), 

trying to pass an array or string, doesn’t work:

'From_x0020_ContactsId': json1, 'From_x0020_ContactsId': json2, 'From_x0020_ContactsId': {'results': ["" + iArray + ""]}, 'From_x0020_ContactsId': {'results': ["" + sArray + ""]}, 'From_x0020_ContactsId': "{'results': [" + fIdArray.join() + "]}", 'From_x0020_ContactsId': {'__metadata': { 'type': 'Collection(Edm.Int32' }, 'results': iArray}, 

always primitive or Edm32 error. Suggestions?