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Filter function will not delete my empty rows - Google App Script

I want to import rows from one google sheet to the other, however source sheet imports a number of empty rows. Now I use a filter function to get rid of these rows but they will not disappear, can anyone tell me why?
var a = SpreadsheetApp.openByUrl("url").getSheetByName("Admin Use Only").getRange(4,1,6,21).getValues();
var b = SpreadsheetApp.getActive().getSheetByName('Credit_Detail');
b.getRange(b.getLastRow() +1, 1, a.length,21).setValues(a);
//filter function below:
var otarget=b.getRange(2,1,b.getLastRow()-1, 26).getValues();
var data=otarget.filter(function(r){
return !r.every(function(cell){
return cell === "";});
});
Logger.log(data);
b.getRange("A2:Z").clearContent();
b.getRange(3,1,data.length,data[0].length).setValues(data);

here's how I would do it. First, create an variable to store the array of the source. then run a for loop scanning the first column for empties. something like: for (var i = 0, i < data.length; i++) { if (data[i][0] != '') { XXXX } }
XXXX means that you can either put a code to create a new set of array which can be passed to the target sheet at once or use append row to transfer non blank rows to the target sheet one by one.
Note: Creating a new array to store non-empty rows would speedup the execution time if you are dealing with large data, thousands of rows.

Tabulator.js: get/select rows on current page

I am using an amazing tabulator plugin for managing tabular data, API is very clear and reliable but i cant do a very simple thing: get/select all rows on current page.
Custom row selection can look like this:
table.selectRow(table.getRows().filter(row => <<Custom Selection>>);
Where Custom selection has to respect the current page, but i dont get from where i can take it.
Maybe i am missing something?

There is no way to do that directly form Tabulator, but is should be fairly easy to do yourself with a bit of JavaScript.
First you want to get the rows that are visible on that page:
var pageRows = table.getRows(true);
Then you want to get the selected rows
var selectedRows = table.getSelectedRows();
then you want to find rows that exist in both arrays, these will be the selected rows on that page:
var rows = selectedRows.filter(value => -1 !== pageRows.indexOf(value));

Assuming the column name of your index is 'id' you can do the following:
var selectedData = table.getSelectedData();
jQuery.map(selectedData, function(value, index) {
console.log(value.id);
});

How to change the active range into an array which can be set by setValues

I've been working on this simple code in google scripts to execute on a button.
I want the user to be able to select two cells side by side, then click the button. The 1st selected cell will be updated with the date, the cell to the right will be incremented by one. So far I've gotten this far:
function increment() {
var ss = SpreadsheetApp.getActiveSpreadsheet();
var activeSheet = ss.getActiveSheet();
var activeValues = activeSheet.getActiveRange().getValues();
var newValues = [[Utilities.formatDate(new Date(), "UTC-8",
"yyyy/MM/dd"),activeValues[1]+1]];
activeValues.setValues(newValues);
}
I think that I need to use setValues on getActiveRange but I'm not sure how to change the active range into an array which can be set by setValues.
I don't think I'm calling the correct element (1st element, second column) with activevalues[1]. Not sure how to call it.
Right now I get error: Cannot find function setValues in object,1.

The error occurs because activeValues is an array of arrays / 2D array but setValues is a method of Class Range.
Assuming that activeValues has the same shape that newValues, to do the minimal changes to your code you could instead of
activeValues.setValues(newValues);
use
activeSheet.getActiveRange().setValues(newValues);

The element from activeValues should be one of these:
Number(activeValues[0][1])
Number(activeValues[1][0])
The choice depends on whether the cells are horizontal or vertical.
And the values are set with activeSheet.getActiveRange().setValues(newValues).

Standard way of building an arbitrary length table in Javascript

I'm receiving data from a websocket (live stream), and trying to put it into a table. I'm currently using the following code:
var table = document.getElementById("websocket-data");
function writeToScreen(message) {
var new_row = table.insertRow(0);
var cell1 = new_row.insertCell(0);
var cell2 = new_row.insertCell(1);
var obj = JSON.parse(message.data);
console.log(obj.value);
cell1.innerHTML = obj.id;
cell2.innerHTML = obj.value;
}
This works, and creates a new row for every JSON packet. The functionality that I am looking for is: On receipt of a JSON, if the id is not in the table, then create a row with id and value, however, if the id is already in the table, simply update the value. I've come across a few ways of doing this, but I'd like to know what the 'proper' way to do it is. I was thinking that perhaps the data should go into an array, and then the array should populate the table, but that would involve repopulating the entire table every time the array changed... I'm happy to use JQuery or similar if necessary.

You could use an array and repopulate the table every time like you said, and if the table will only ever be small then you may not run into issues with that.
One possible alternative of many is maintaining an object in the background with your ids as keys and then store the value and the table row index as values.
Something like:
var tableStore = {};
function recieveMessage(message) {
var obj = JSON.parse(message);
// if the id is not in the tableStore, add it!
if (tableStore[obj.id] === undefined) {
// insert new row into table and save the index into `newTableRowIndex`
// store a blank value (updated below) and the index in the table where it will be displayed
tableStore[obj.id] = {value: undefined, tableIndex: newTableRowIndex};
}
// if the value recieved is different than the stored value, update the row
if (obj.value !== tableStore[obj.id].value) {
tableStore[obj.id].value = obj.value; // store the new value
var row = getTableRow(tableStore[obj.id].tableIndex); // your own function to get the row based on index
// update the row to display the new information
}
}
This could be improved and made to be more organized but you should get the idea.
This way it would only update anything in the display if the new information recieved is different than the old information already stored.
This way should also perform better than using an array would if the table has the potential to get very large as you would not need to search through the entire array every time to see if the id is already stored or not. You would simply access the tableStore entry directly using the id.

Datatable : add row and check added row's index

I want to check whether the newly added row appear in first page or not. One way of doing it is get the index, but I wonder why it doesn't work, the index for me is not accurate at all.
function add_row(name, time_taken, attempts) {
var t = $('#dashboard').DataTable();
var node = '';
node = t.row.add([
'',
name,
time_taken,
attempts
]).draw().node();
$(node).attr('id', concatSpaces(name)).hide().fadeIn('slow');
var index = t.row('#' + concatSpaces(name)).index() // doesn't work
any thought? stuck for 2 hours long!

API method row().index() returns internal index which doesn't mean row position in the table based on current sorting column and method.
You need to use the code below instead to locate index of the row based on current sorting column and method:
var index = table.$('tr').index(node);
See this jsFiddle for code and demonstration.