diff --git a/src/func_plot.rs b/src/func_plot.rs
index 67cffa0..6fc826c 100644
--- a/src/func_plot.rs
+++ b/src/func_plot.rs
@@ -36,14 +36,16 @@ pub fn draw(
 
     chart.configure_mesh().x_labels(3).y_labels(3).draw()?;
 
-    let data = (1..=resolution)
+    let data: Vec<(f32, f32)> = (1..=resolution)
         .map(|x| ((x as f32 / resolution as f32) * (&absrange)) + &min_x)
         .map(|x| (x, func(x as f64) as f32))
-        .filter(|(_, y)| &min_y <= y && y <= &max_y);
+        .filter(|(_, y)| &min_y <= y && y <= &max_y)
+        .collect();
 
     chart.draw_series(LineSeries::new(data, &RED))?;
 
-    let (data2, area) = integral_rectangles(min_x, step, num_interval, &func); // Get rectangle coordinates and the total area
+    let (data2, area): (Vec<(f32, f32, f32)>, f32) =
+        integral_rectangles(min_x, step, num_interval, &func); // Get rectangle coordinates and the total area
 
     // Draw rectangles
     chart.draw_series(
@@ -54,7 +56,7 @@ pub fn draw(
 
     root.present()?;
     let output = chart.into_coord_trans();
-    return Ok(((output), area));
+    return Ok((output, area));
 }
 
 // Creates and does the math for creating all the rectangles under the graph
diff --git a/src/lib.rs b/src/lib.rs
index 538ab1c..e0136b5 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -25,7 +25,7 @@ pub struct Point {
 impl Chart {
     pub fn draw(
         canvas: HtmlCanvasElement,
-        func: &str,
+        func_str: &str,
         min_x: f32,
         max_x: f32,
         min_y: f32,
@@ -33,9 +33,9 @@ impl Chart {
         num_interval: usize,
         resolution: i32,
     ) -> Result<Chart, JsValue> {
-        let output = func_plot::draw(
+        let draw_output = func_plot::draw(
             canvas,
-            func,
+            func_str,
             min_x,
             max_x,
             min_y,
@@ -44,15 +44,16 @@ impl Chart {
             resolution,
         )
         .map_err(|err| err.to_string())?;
-        let map_coord = output.0;
-        Ok(Chart {
+        let map_coord = draw_output.0;
+
+        return Ok(Chart {
             convert: Box::new(move |coord| map_coord(coord).map(|(x, y)| (x.into(), y.into()))),
-            area: output.1,
-        })
+            area: draw_output.1,
+        });
     }
 
-    pub fn get_area(&self) -> Result<f32, JsValue> {
-        return Ok(self.area);
+    pub fn get_area(&self) -> f32 {
+        return self.area;
     }
 
     pub fn coord(&self, x: i32, y: i32) -> Option<Point> {
diff --git a/www/index.js b/www/index.js
index 447e337..8a93e6b 100644
--- a/www/index.js
+++ b/www/index.js
@@ -1,5 +1,3 @@
-// If you only use `npm` you can simply
-// import { Chart } from "wasm-demo" and remove `setup` call from `bootstrap.js`.
 class Chart {}
 
 const canvas = document.getElementById("canvas");
@@ -57,7 +55,7 @@ function onMouseMove(event) {
     if (chart) {
 		var text = "Mouse is outside Chart.";
 
-		if(event.target == canvas) {
+		if (event.target == canvas) {
 			let actualRect = canvas.getBoundingClientRect();
 			let logicX = event.offsetX * canvas.width / actualRect.width;
 			let logicY = event.offsetY * canvas.height / actualRect.height;
@@ -72,10 +70,9 @@ function onMouseMove(event) {
 
 function updatePlot() {
     status.innerText = `Rendering y=${math_function.value}...`;
-    chart = null;
+    
     const start = performance.now();
-
-	chart = Chart.draw(canvas, math_function.value, Number(minX.value), Number(maxX.value), Number(minY.value), Number(maxY.value), Number(num_interval.value), Number(resolution.value));
+    chart = Chart.draw(canvas, math_function.value, Number(minX.value), Number(maxX.value), Number(minY.value), Number(maxY.value), Number(num_interval.value), Number(resolution.value));
     const end = performance.now();
 
     area_msg.innerText = `Estimated Area: ${chart.get_area()}`;