diff --git a/data_visualization/js/app.js b/data_visualization/js/app.js
new file mode 100644
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+++ b/data_visualization/js/app.js
@@ -0,0 +1,173 @@
+import { fetchSensorData } from './api.js';
+
+/**
+ * @typedef {Object} SensorData
+ * @property {string} timestamp
+ * @property {string} location_id
+ * @property {number} temperature
+ * @property {number} humidity
+ * @property {number} light
+ */
+
+let allData = [];
+let chartInstances = {};
+
+/**
+ * Initialisiert UI-Elemente, ruft Daten ab und rendert Diagramme.
+ * Wird beim Laden des Fensters aufgerufen.
+ */
+export async function initApp() {
+  try {
+    const data = await fetchSensorData();
+    if (!Array.isArray(data)) {
+      console.error('Ungültige Datenstruktur von /data');
+      return;
+    }
+    allData = data;
+    initializeFilters();
+    renderCharts(data);
+  } catch (error) {
+    console.error('Fehler beim Initialisieren der Anwendung:', error);
+  }
+}
+
+/**
+ * Initialisiert Datumsauswahl- und Filter-Events.
+ */
+function initializeFilters() {
+  const startInput = document.getElementById('filter-start');
+  const endInput = document.getElementById('filter-end');
+
+  [startInput, endInput].forEach((input) => {
+    if (input) {
+      input.addEventListener('change', () => {
+        const startDate = new Date(startInput?.value);
+        const endDate = new Date(endInput?.value);
+        const filtered = filterDataByDate(allData, startDate, endDate);
+        updateCharts(filtered);
+      });
+    }
+  });
+}
+
+/**
+ * Filtert Daten basierend auf Start- und Enddatum.
+ * @param {SensorData[]} data
+ * @param {Date} start
+ * @param {Date} end
+ * @returns {SensorData[]}
+ */
+function filterDataByDate(data, start, end) {
+  if (!(start instanceof Date) || !(end instanceof Date)) return data;
+  return data.filter(({ timestamp }) => {
+    const t = new Date(timestamp);
+    return t >= start && t <= end;
+  });
+}
+
+/**
+ * Rendert initiale Diagramme.
+ * @param {SensorData[]} data
+ */
+function renderCharts(data) {
+  const ctxTemp = document.getElementById('chart-temperature');
+  const ctxHum = document.getElementById('chart-humidity');
+  const ctxLight = document.getElementById('chart-light');
+
+  const timestamps = data.map(d => new Date(d.timestamp).toLocaleTimeString());
+
+  chartInstances.temperature = new Chart(ctxTemp, {
+    type: 'line',
+    data: {
+      labels: timestamps,
+      datasets: [{
+        label: 'Temperatur (°C)',
+        data: data.map(d => d.temperature),
+        borderColor: '#FF5733',
+        backgroundColor: 'rgba(255, 87, 51, 0.1)',
+        tension: 0.3,
+      }]
+    },
+    options: baseChartOptions('Temperaturverlauf')
+  });
+
+  chartInstances.humidity = new Chart(ctxHum, {
+    type: 'line',
+    data: {
+      labels: timestamps,
+      datasets: [{
+        label: 'Feuchtigkeit (%)',
+        data: data.map(d => d.humidity),
+        borderColor: '#33A1FF',
+        backgroundColor: 'rgba(51, 161, 255, 0.1)',
+        tension: 0.3,
+      }]
+    },
+    options: baseChartOptions('Feuchtigkeitsverlauf')
+  });
+
+  chartInstances.light = new Chart(ctxLight, {
+    type: 'line',
+    data: {
+      labels: timestamps,
+      datasets: [{
+        label: 'Lichtintensität (lx)',
+        data: data.map(d => d.light),
+        borderColor: '#FFC300',
+        backgroundColor: 'rgba(255, 195, 0, 0.1)',
+        tension: 0.3,
+      }]
+    },
+    options: baseChartOptions('Lichtintensität')
+  });
+}
+
+/**
+ * Options-Vorlage für Diagramme.
+ * @param {string} title
+ * @returns {object}
+ */
+function baseChartOptions(title) {
+  return {
+    responsive: true,
+    maintainAspectRatio: false,
+    interaction: { mode: 'index', intersect: false },
+    plugins: {
+      title: { display: true, text: title },
+      tooltip: { enabled: true },
+      legend: { display: true }
+    },
+    scales: {
+      x: { display: true, title: { display: true, text: 'Zeit' } },
+      y: { display: true }
+    }
+  };
+}
+
+/**
+ * Aktualisiert Diagramme auf Basis neuer Filter oder Daten.
+ * @param {SensorData[]} filteredData
+ */
+export function updateCharts(filteredData) {
+  const timestamps = filteredData.map(d => new Date(d.timestamp).toLocaleTimeString());
+
+  if (chartInstances.temperature) {
+    chartInstances.temperature.data.labels = timestamps;
+    chartInstances.temperature.data.datasets[0].data = filteredData.map(d => d.temperature);
+    chartInstances.temperature.update();
+  }
+
+  if (chartInstances.humidity) {
+    chartInstances.humidity.data.labels = timestamps;
+    chartInstances.humidity.data.datasets[0].data = filteredData.map(d => d.humidity);
+    chartInstances.humidity.update();
+  }
+
+  if (chartInstances.light) {
+    chartInstances.light.data.labels = timestamps;
+    chartInstances.light.data.datasets[0].data = filteredData.map(d => d.light);
+    chartInstances.light.update();
+  }
+}
+
+window.addEventListener('load', initApp);
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