diff --git a/src/qrcode.js b/src/qrcode.js
index a83bddef..ad4f48d2 100644
--- a/src/qrcode.js
+++ b/src/qrcode.js
@@ -15,7 +15,7 @@
 */
 
 
-var qrcode = {};
+let qrcode = {};
 qrcode.imagedata = null;
 qrcode.width = 0;
 qrcode.height = 0;
@@ -90,10 +90,10 @@ qrcode.captureToCanvas = function()
 
 qrcode.setWebcam = function(videoId)
 {
-    var n=navigator;
+    let n=navigator;
     qrcode.video=document.getElementById(videoId);
 
-    var options = true;
+    let options = true;
     if(navigator.mediaDevices && navigator.mediaDevices.enumerateDevices)
     {
         try{
@@ -142,13 +142,13 @@ qrcode.decode = function(src){
     {
         if(qrcode.canvas_qr2)
         {
-            var canvas_qr = qrcode.canvas_qr2;
-            var context = qrcode.qrcontext2;
+            let canvas_qr = qrcode.canvas_qr2;
+            let context = qrcode.qrcontext2;
         }	
         else
         {
-            var canvas_qr = document.getElementById("qr-canvas");
-            var context = canvas_qr.getContext('2d');
+            let canvas_qr = document.getElementById("qr-canvas");
+            let context = canvas_qr.getContext('2d');
         }
         qrcode.width = canvas_qr.width;
         qrcode.height = canvas_qr.height;
@@ -160,25 +160,25 @@ qrcode.decode = function(src){
     }
     else
     {
-        var image = new Image();
+        let image = new Image();
         image.crossOrigin = "Anonymous";
         image.onload=function(){
             //var canvas_qr = document.getElementById("qr-canvas");
-            var canvas_out = document.getElementById("out-canvas");
+            let canvas_out = document.getElementById("out-canvas");
             if(canvas_out!=null)
             {
-                var outctx = canvas_out.getContext('2d');
+                let outctx = canvas_out.getContext('2d');
                 outctx.clearRect(0, 0, 320, 240);
                 outctx.drawImage(image, 0, 0, 320, 240);
             }
 
-            var canvas_qr = document.createElement('canvas');
-            var context = canvas_qr.getContext('2d');
-            var nheight = image.height;
-            var nwidth = image.width;
+            let canvas_qr = document.createElement('canvas');
+            let context = canvas_qr.getContext('2d');
+            let nheight = image.height;
+            let nwidth = image.width;
             if(image.width*image.height>qrcode.maxImgSize)
             {
-                var ir = image.width / image.height;
+                let ir = image.width / image.height;
                 nheight = Math.sqrt(qrcode.maxImgSize/ir);
                 nwidth=ir*nheight;
             }
@@ -221,13 +221,13 @@ qrcode.decode = function(src){
 
 qrcode.isUrl = function(s)
 {
-    var regexp = /(ftp|http|https):\/\/(\w+:{0,1}\w*@)?(\S+)(:[0-9]+)?(\/|\/([\w#!:.?+=&%@!\-\/]))?/;
+    let regexp = /(ftp|http|https):\/\/(\w+:{0,1}\w*@)?(\S+)(:[0-9]+)?(\/|\/([\w#!:.?+=&%@!\-\/]))?/;
     return regexp.test(s);
 }
 
 qrcode.decode_url = function (s)
 {
-  var escaped = "";
+  let escaped = "";
   try{
     escaped = escape( s );
   }
@@ -258,18 +258,18 @@ qrcode.decode_utf8 = function ( s )
 
 qrcode.process = function(ctx){
     
-    var start = new Date().getTime();
+    let start = new Date().getTime();
 
-    var image = qrcode.grayScaleToBitmap(qrcode.grayscale());
+    let image = qrcode.grayScaleToBitmap(qrcode.grayscale());
     //var image = qrcode.binarize(128);
     
     if(qrcode.debug)
     {
-        for (var y = 0; y < qrcode.height; y++)
+        for (let y = 0; y < qrcode.height; y++)
         {
-            for (var x = 0; x < qrcode.width; x++)
+            for (let x = 0; x < qrcode.width; x++)
             {
-                var point = (x * 4) + (y * qrcode.width * 4);
+                let point = (x * 4) + (y * qrcode.width * 4);
                 qrcode.imagedata.data[point] = image[x+y*qrcode.width]?0:0;
                 qrcode.imagedata.data[point+1] = image[x+y*qrcode.width]?0:0;
                 qrcode.imagedata.data[point+2] = image[x+y*qrcode.width]?255:0;
@@ -280,17 +280,17 @@ qrcode.process = function(ctx){
     
     //var finderPatternInfo = new FinderPatternFinder().findFinderPattern(image);
     
-    var detector = new Detector(image);
+    let detector = new Detector(image);
 
-    var qRCodeMatrix = detector.detect();
+    let qRCodeMatrix = detector.detect();
     
     if(qrcode.debug)
     {
-        for (var y = 0; y < qRCodeMatrix.bits.Height; y++)
+        for (let y = 0; y < qRCodeMatrix.bits.Height; y++)
         {
-            for (var x = 0; x < qRCodeMatrix.bits.Width; x++)
+            for (let x = 0; x < qRCodeMatrix.bits.Width; x++)
             {
-                var point = (x * 4*2) + (y*2 * qrcode.width * 4);
+                let point = (x * 4*2) + (y*2 * qrcode.width * 4);
                 qrcode.imagedata.data[point] = qRCodeMatrix.bits.get_Renamed(x,y)?0:0;
                 qrcode.imagedata.data[point+1] = qRCodeMatrix.bits.get_Renamed(x,y)?0:0;
                 qrcode.imagedata.data[point+2] = qRCodeMatrix.bits.get_Renamed(x,y)?255:0;
@@ -300,17 +300,17 @@ qrcode.process = function(ctx){
     }
     
     
-    var reader = Decoder.decode(qRCodeMatrix.bits);
-    var data = reader.DataByte;
-    var str="";
-    for(var i=0;i<data.length;i++)
+    let reader = Decoder.decode(qRCodeMatrix.bits);
+    let data = reader.DataByte;
+    let str="";
+    for(let i=0;i<data.length;i++)
     {
-        for(var j=0;j<data[i].length;j++)
+        for(let j=0;j<data[i].length;j++)
             str+=String.fromCharCode(data[i][j]);
     }
     
-    var end = new Date().getTime();
-    var time = end - start;
+    let end = new Date().getTime();
+    let time = end - start;
     console.log(time);
     
     return qrcode.decode_utf8(str);
@@ -324,18 +324,18 @@ qrcode.getPixel = function(x,y){
     if (qrcode.height < y) {
         throw "point error";
     }
-    var point = (x * 4) + (y * qrcode.width * 4);
-    var p = (qrcode.imagedata.data[point]*33 + qrcode.imagedata.data[point + 1]*34 + qrcode.imagedata.data[point + 2]*33)/100;
+    let point = (x * 4) + (y * qrcode.width * 4);
+    let p = (qrcode.imagedata.data[point]*33 + qrcode.imagedata.data[point + 1]*34 + qrcode.imagedata.data[point + 2]*33)/100;
     return p;
 }
 
 qrcode.binarize = function(th){
-    var ret = new Array(qrcode.width*qrcode.height);
-    for (var y = 0; y < qrcode.height; y++)
+    let ret = new Array(qrcode.width*qrcode.height);
+    for (let y = 0; y < qrcode.height; y++)
     {
-        for (var x = 0; x < qrcode.width; x++)
+        for (let x = 0; x < qrcode.width; x++)
         {
-            var gray = qrcode.getPixel(x, y);
+            let gray = qrcode.getPixel(x, y);
             
             ret[x+y*qrcode.width] = gray<=th?true:false;
         }
@@ -345,29 +345,29 @@ qrcode.binarize = function(th){
 
 qrcode.getMiddleBrightnessPerArea=function(image)
 {
-    var numSqrtArea = 4;
+    let numSqrtArea = 4;
     //obtain middle brightness((min + max) / 2) per area
-    var areaWidth = Math.floor(qrcode.width / numSqrtArea);
-    var areaHeight = Math.floor(qrcode.height / numSqrtArea);
-    var minmax = new Array(numSqrtArea);
-    for (var i = 0; i < numSqrtArea; i++)
+    let areaWidth = Math.floor(qrcode.width / numSqrtArea);
+    let areaHeight = Math.floor(qrcode.height / numSqrtArea);
+    let minmax = new Array(numSqrtArea);
+    for (let i = 0; i < numSqrtArea; i++)
     {
         minmax[i] = new Array(numSqrtArea);
-        for (var i2 = 0; i2 < numSqrtArea; i2++)
+        for (let i2 = 0; i2 < numSqrtArea; i2++)
         {
             minmax[i][i2] = new Array(0,0);
         }
     }
-    for (var ay = 0; ay < numSqrtArea; ay++)
+    for (let ay = 0; ay < numSqrtArea; ay++)
     {
-        for (var ax = 0; ax < numSqrtArea; ax++)
+        for (let ax = 0; ax < numSqrtArea; ax++)
         {
             minmax[ax][ay][0] = 0xFF;
-            for (var dy = 0; dy < areaHeight; dy++)
+            for (let dy = 0; dy < areaHeight; dy++)
             {
-                for (var dx = 0; dx < areaWidth; dx++)
+                for (let dx = 0; dx < areaWidth; dx++)
                 {
-                    var target = image[areaWidth * ax + dx+(areaHeight * ay + dy)*qrcode.width];
+                    let target = image[areaWidth * ax + dx+(areaHeight * ay + dy)*qrcode.width];
                     if (target < minmax[ax][ay][0])
                         minmax[ax][ay][0] = target;
                     if (target > minmax[ax][ay][1])
@@ -377,14 +377,14 @@ qrcode.getMiddleBrightnessPerArea=function(image)
             //minmax[ax][ay][0] = (minmax[ax][ay][0] + minmax[ax][ay][1]) / 2;
         }
     }
-    var middle = new Array(numSqrtArea);
-    for (var i3 = 0; i3 < numSqrtArea; i3++)
+    let middle = new Array(numSqrtArea);
+    for (let i3 = 0; i3 < numSqrtArea; i3++)
     {
         middle[i3] = new Array(numSqrtArea);
     }
-    for (var ay = 0; ay < numSqrtArea; ay++)
+    for (let ay = 0; ay < numSqrtArea; ay++)
     {
-        for (var ax = 0; ax < numSqrtArea; ax++)
+        for (let ax = 0; ax < numSqrtArea; ax++)
         {
             middle[ax][ay] = Math.floor((minmax[ax][ay][0] + minmax[ax][ay][1]) / 2);
             //Console.out.print(middle[ax][ay] + ",");
@@ -398,23 +398,23 @@ qrcode.getMiddleBrightnessPerArea=function(image)
 
 qrcode.grayScaleToBitmap=function(grayScale)
 {
-    var middle = qrcode.getMiddleBrightnessPerArea(grayScale);
-    var sqrtNumArea = middle.length;
-    var areaWidth = Math.floor(qrcode.width / sqrtNumArea);
-    var areaHeight = Math.floor(qrcode.height / sqrtNumArea);
+    let middle = qrcode.getMiddleBrightnessPerArea(grayScale);
+    let sqrtNumArea = middle.length;
+    let areaWidth = Math.floor(qrcode.width / sqrtNumArea);
+    let areaHeight = Math.floor(qrcode.height / sqrtNumArea);
 
-    var buff = new ArrayBuffer(qrcode.width*qrcode.height);
-    var bitmap = new Uint8Array(buff);
+    let buff = new ArrayBuffer(qrcode.width*qrcode.height);
+    let bitmap = new Uint8Array(buff);
 
     //var bitmap = new Array(qrcode.height*qrcode.width);
     
-    for (var ay = 0; ay < sqrtNumArea; ay++)
+    for (let ay = 0; ay < sqrtNumArea; ay++)
     {
-        for (var ax = 0; ax < sqrtNumArea; ax++)
+        for (let ax = 0; ax < sqrtNumArea; ax++)
         {
-            for (var dy = 0; dy < areaHeight; dy++)
+            for (let dy = 0; dy < areaHeight; dy++)
             {
-                for (var dx = 0; dx < areaWidth; dx++)
+                for (let dx = 0; dx < areaWidth; dx++)
                 {
                     bitmap[areaWidth * ax + dx+ (areaHeight * ay + dy)*qrcode.width] = (grayScale[areaWidth * ax + dx+ (areaHeight * ay + dy)*qrcode.width] < middle[ax][ay])?true:false;
                 }
@@ -426,15 +426,15 @@ qrcode.grayScaleToBitmap=function(grayScale)
 
 qrcode.grayscale = function()
 {
-    var buff = new ArrayBuffer(qrcode.width*qrcode.height);
-    var ret = new Uint8Array(buff);
+    let buff = new ArrayBuffer(qrcode.width*qrcode.height);
+    let ret = new Uint8Array(buff);
     //var ret = new Array(qrcode.width*qrcode.height);
     
-    for (var y = 0; y < qrcode.height; y++)
+    for (let y = 0; y < qrcode.height; y++)
     {
-        for (var x = 0; x < qrcode.width; x++)
+        for (let x = 0; x < qrcode.width; x++)
         {
-            var gray = qrcode.getPixel(x, y);
+            let gray = qrcode.getPixel(x, y);
             
             ret[x+y*qrcode.width] = gray;
         }