Trouble writing result to a spreadsheet using batch update

Question

I've created a script to scrape two fields from a webpage using google apps script. The script seems to be working properly but it writes results in a spreadsheet on a per line basis.

What I did is grab the links of all the shops from landing page and then reuse the links within another function to parse shop name and website link from innerpages. Although the two fields are also available in landing page, I wish to parse them from their innerpages.

However, I wish to write the result in the spreadsheet doing batch update. How can I achieve that?

Current approach:

function parseYellowpages() {
  var options = {
    "method" : "GET",
    "headers" : {
        "User-Agent": "Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like  Gecko) Chrome/88.0.4324.150 Safari/537.36"
     }
    };
  var ss = SpreadsheetApp.getActiveSpreadsheet();
  var activeSheet = ss.getSheetByName('Sheet1');
  var base = "https://www.yellowpages.com"
  var webURL = "https://www.yellowpages.com/search?search_terms=pizza&geo_location_terms=New+York%2C+NY";

  var row = 1;

  var response = UrlFetchApp.fetch(webURL,options);
  var $ = Cheerio.load(response.getContentText()); 

  const items = $("[class='result'] [class='info']");
  for (i=0;i<items.length;i++){
      var shopLink = base + $(items[i]).find('h2[class="n"] > a.business-name').attr('href');
      var resultContainer;
      resultContainer = getInnerpageInfo(shopLink,options);
      activeSheet.getRange(row,1).setValue(resultContainer[0]);
      activeSheet.getRange(row,2).setValue(resultContainer[1]);
      console.log(resultContainer[0],resultContainer[1]);
      row++;
    };
}

function getInnerpageInfo(innerLink,options) {
    var response = UrlFetchApp.fetch(innerLink,options);
    var $ = Cheerio.load(response.getContentText()); 
    var shopName = $('.sales-info > h1').first().text();
    var website = $('a.website-link').first().attr('href');
    return [shopName,website];

}

How to write result to a spreadsheet doing batch update?

Answer 1

You can dramatically improve performance by replacing repeated .setValue() calls with one .setValues() call that writes all results to the spreadsheet in one batch.

To collect the results, push them into an array one by one in the loop, or replace the loop with Element.map(), like this:

  const result = items.map((index, item) => {
    const path = $(item).find('h2[class="n"] > a.business-name').attr('href');
    const shopLink = base + path;
    return [getInnerpageInfo(shopLink, options)];
  }).get();

To write the results, get a range whose size matches the dimensions of the results and use .setValues(), like this:

  activeSheet.getRange('A1')
    .offset(0, 0, result.length, result[0].length)
    .setValues(result);

The reason why the code in the question does not seem to be doing anything for some time is that Google Apps Script caches writes to the spreadsheet. In many cases, all the writes only get executed when the script terminates.

If you need to apply pending writes immediately, use SpreadsheetApp.flush().

Also see Apps Script best practices and UrlFetchApp.fetchAll().