get value in one column in spreadsheet using google apps script

If you use simply :

var values = SpreadsheetApp.getActiveSheet().getDataRange().getValues()

You will get a 2 Dimension array of all the data in the sheet indexed by rows and columns.

So to get the value in column A, row1 you use values[0][0] , values[1][0] for columnA, row 2, values[0][2] for column C row1, etc…

If you need to iterate in a for loop (in a single column) :

for (n = 0; n < values.length; ++n) {
    var cell = values[n][x] ; // x is the index of the column starting from 0
}

If you need to iterate in a for loop (in a single row) :

for (n = 0; n < values[0].length; ++n) {
    var cell = values[x][n] ; // x is the index of the row starting from 0
}