Google Script version of VLookup (More Efficient Method?)

Question

I\'m trying to put together a function that will allow me to pull a column\'s info from one sheet to another based on a key column. This would work similar to an index match or

Answer 1

Issue:

• Slow script:

  • O(n²): For every element in array 1, the array 2 is iterated from top to bottom. Even after finding a match in array 2, the loop is not broken(break), but the inner loop is completed until the end of the array2 unnecessarily.

  • getValues() is requested twice for two columns of the same sheet. Contact with spreadsheet is costly. So, limiting it is necessary.

Solution:

One possible solution to achieve O(n):

• Create a new object using array 1 with key as 'the value to look for'. Then it's possible to directly access the value in this object each time for each value in array 2.

Sample script:

const ss = SpreadsheetApp.getActive();
/**
 * @param {GoogleAppsScript.Spreadsheet.Sheet} fromSht -Sheet to import from
 * @param {GoogleAppsScript.Spreadsheet.Sheet} toSht -Sheet to import to
 * @param {Number} fromCompCol -Column number of fromSht to compare
 * @param {Number} toCompCol -Column number of toSht to compare
 * @param {Number} fromCol -Column number of fromSht to get result
 * @param {Number} toCol -Column number of toSht to get result
 */
function vlookup_2(
  fromSht = ss.getSheetByName('Sheet1'),
  toSht = ss.getSheetByName('Sheet2'),
  fromCompCol = 1,
  toCompCol = 1,
  fromCol = 2,
  toCol = 2
) {
  const toShtLr = toSht.getLastRow();
  const toCompArr = toSht.getRange(2, toCompCol, toShtLr - 1, 1).getValues();
  const fromArr = fromSht.getDataRange().getValues();
  fromCompCol--;
  fromCol--;

  /*Create a hash object of fromSheet*/
  const obj1 = fromArr.reduce((obj, row) => {
    let el = row[fromCompCol];
    el in obj ? null : (obj[el] = row[fromCol]);
    return obj;
  }, {});

  //Paste to column
  toSht
    .getRange(2, toCol, toShtLr - 1, 1)
    .setValues(toCompArr.map(row => (row[0] in obj1 ? [obj1[row[0]]] : [null])));
}

Performance:

• ~5s for 10000 rows in sheet1 and 10000 rows in sheet 2

References:

• Time complexity
• Hash map