posToRef

converts a position of a cell into a cell reference

string posToRef(number row1,number row2,number column1,number column2,string sheet);

row1	number	the number index of the first row
row2	number	the number index of the second row
column1	number	the number index of the first column
column2	number	the number index of the second column
sheet	string	the name of the sheet

string

a cell reference

Example

$$('ssheet').posToRef(1, 1); // A1
$$('ssheet').posToRef(1, 1, 2, 2); // A1:B2
 
$$('ssheet').posToRef(1, 1, null, null, "Sheet1"); // Sheet1!A1
//or 
$$('ssheet').posToRef(1, 1, 1, 1, "Sheet1"); // Sheet1!A1
 
$$('ssheet').posToRef(1, 1, 2, 2, "Sheet1"); // Sheet1!A1:B2

Details

In case you need to convert the column letter into the index and vice versa, you can do it in the following way:

var ssheet = webix.ui({
    view:"spreadsheet", 
    toolbar:"full", 
    data:spreadsheet_data
}); 
 
const col = 28;
 
// the number to the letter
const colLetter = ssheet.posToRef(1, col).split("1")[0];
webix.message(colLetter);
 
// the letter to the number
webix.message(ssheet.refToPos(colLetter+1)[1]);