Append new data to sheet without overwriting in GAS - google-apps-script

Question

I need to figure out what to add to my script to add new data to the end of my sheet without overwriting the existing data. I'm a total beginner and have researched this, but can't seem to put the code together. Here is my script:
function myFunction() {
var url = "xxxxxxxx"
var response = UrlFetchApp.fetch(url)
var data = response.getContentText()
var result = JSON.parse(data)
var sheet = SpreadsheetApp.getActiveSheet()
sheet.clear()
var headerRow = ['Title','Brand','UPC','In Stock','Stock Level','Price','Seller','Next Day','Ship to Home', 'Link']
sheet.appendRow(headerRow)
for(var i=0; i<result.category_results.length; i++){
var row = [result.category_results[i].product.title, result.category_results[i].product.brand, result.category_results[i].product.upc,result.category_results[i].inventory.in_stock,
result.category_results[i].inventory.stock_level, result.category_results[i].offers.primary.price, result.category_results[i].offers.primary.seller_name,
result.category_results[i].fulfillment.next_day_shipping_eligible, result.category_results[i].fulfillment.ship_to_home, result.category_results[i].product.link]
sheet.appendRow(row)
}
}

Answer 1

Modification points:
In your script, the sheet is cleared every run by sheet.clear(). By this, the existing values are always deleted, and the sheet is overwritten by the new values. I think that this is the reason of your issue.
In your script, appendRow is used in a loop. In this case, the process cost will be high.
In order to append the new values to the sheet, I would like to propose the following flow.
Retrieve values. (This is your script.)
Check whether there are the existing values in the sheet.
Create an array for putting the values to the sheet.
Put the values using the array.
In this case, setValues is used instead of appendRow.
When above points are reflected to your script, it becomes as follows.
Modified script:
function myFunction() {
// 1. Retrieve values. (This is your script.)
var url = "xxxxxxxx";
var response = UrlFetchApp.fetch(url);
var data = response.getContentText();
var result = JSON.parse(data);
// 2. Check whether there are the existing values in the sheet.
var sheet = SpreadsheetApp.getActiveSheet();
var lastRow = sheet.getLastRow();
if (lastRow == 0) {
var headerRow = ['Title','Brand','UPC','In Stock','Stock Level','Price','Seller','Next Day','Ship to Home', 'Link'];
sheet.appendRow(headerRow);
}
// 3. Create an array for putting the values to the sheet.
var values = []
for(var i=0; i<result.category_results.length; i++){
var row = [result.category_results[i].product.title, result.category_results[i].product.brand, result.category_results[i].product.upc,result.category_results[i].inventory.in_stock,
result.category_results[i].inventory.stock_level, result.category_results[i].offers.primary.price, result.category_results[i].offers.primary.seller_name,
result.category_results[i].fulfillment.next_day_shipping_eligible, result.category_results[i].fulfillment.ship_to_home, result.category_results[i].product.link];
values.push(row);
}
// 4. Put the values using the array.
sheet.getRange(lastRow + 1, 1, values.length, values[0].length).setValues(values);
}
Note:
In this modified script, it supposes that your values can be retrieved with row. Please be careful this.
References:
setValues(values)
Benchmark: Reading and Writing Spreadsheet using Google Apps Script