Get XML File - Find Duplicate before adding new rows - google-apps-script

Question

I'm French and beginner in the app script.
My Problem:
I get data from a "var resultat = UrlFetchApp.fetch(url).getContentText();" that gives me an XML file
I want to add the result in my spreadsheet BUT before I would like to know if the row already exists in my spreadsheet.
I try to do this:
function GetMeteo() {
url = "http://www.yr.no/place/France/Alsace/Strasbourg/forecast_hour_by_hour.xml";
var resultat = UrlFetchApp.fetch(url).getContentText();
var root = XmlService.parse(resultat).getRootElement();
var entries = root.getChild('forecast').getChild('tabular').getChildren();
var sheet = SpreadsheetApp.getActiveSheet();
var data = sheet.getDataRange().getValues();
var newData = new Array();
for (var i =0 ; i < entries.length; i++) {
var heure = entries[i].getAttribute('from').getValue();
var precipitation = entries[i].getChild('precipitation').getAttribute('value').getValue();
var windDirection = entries[i].getChild('windDirection').getAttribute('deg').getValue();
var windSpeed = entries[i].getChild('windSpeed').getAttribute('mps').getValue();
var temperature = entries[i].getChild('temperature').getAttribute('value').getValue();
var pressure = entries[i].getChild('pressure').getAttribute('value').getValue();
var duplicate = -1;
Données.activate();
var data = Données.getDataRange().getValues();
for (j in data) {
if (data[j][0] == heure) {
duplicate = j;
}
else {
duplicate = -1;
}
}
if (NumLigne == -1) {
data.push({heure,precipitation,windDirection,windSpeed,temperature,pressure});
}
else {
data[NumLigne].push({heure,precipitation,windDirection,windSpeed,temperature,pressure});
}
}
But the DataPush does not work.