Sheet().getRange(ARRAY). code example
Example 1: google script get sheet size
var lastColumn = sheet.getLastColumn();
// Returns the position of the last column that has content.
Example 2: google sheets get ranges
//getRange(row, column, optNumRows, optNumColumns);
Sheet.getRange(1,1,1,12);
//row --- int --- top row of the range
//column --- int--- leftmost column of the range
//optNumRows --- int --- number of rows in the range.
//optNumColumns --- int --- number of columns in the range