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JavaScript

Posted by Grace Nellore
Grace Nellore
9,447 Points

Uncaught ReferenceError: e is not defined (chrome & safari)

Hello, I was wondering if anyone else has come across this issue, and has any ideas?

In jQuery Basics > Creating a Simple Drawing Application > Perform: Part 5 (https://teamtreehouse.com/library/jquery-basics/creating-a-simple-drawing-application/perform-part-5)

I am getting following errors:

  1. Uncaught TypeError: Cannot read property 'offsetX' of undefined
  2. Uncaught ReferenceError: e is not defined

Code so far (~6:19m in video):

// Problem: No user interaction causes no change to application
// Solution: When user interacts cause changes appropriately

var color = $(".selected").css("background-color");
var $canvas = $("canvas");
var context = $canvas[0].getContext("2d");
var lastEvent; // <--initializing lastEvent to "{offsetX:0, offsetY:0" addressed 1st issue

// When clicking on control list items
$(".controls").on("click", "li", function(){
  // Deselect sibling elements
  $(this).siblings().removeClass("selected");
  // Select clicked element
  $(this).addClass("selected");
  // Cache current color
  color = $(this).css("background-color");
});


// When "New Color" is pressed
$("#revealColorSelect").click(function(){
  // Show color select or hide color select
  changeColor();
  $("#colorSelect").toggle();
})

// Update the new color span
function changeColor() {
  var r = $("#red").val();
  var g = $("#green").val();
  var b = $("#blue").val();
  $("#newColor").css("background-color", "rgb(" + r + "," + g + "," + b + ")");
}

// When color sliders change
$("input[type=range]").change(changeColor);

// When "Add Color" is pressed
$("#addNewColor").click(function(){
  // Append the color to the controls
  var $newColor = $("<li></li>");
  $newColor.css("background-color", $("#newColor").css("background-color"));
  $(".controls ul").append($newColor);
  // Select the new color

});

// On mouse events on the canvas
$canvas.mousedown(function(e){
  lastEvent = e;
}).mousemove(function(){
  // Draw lines
  context.beginPath();
  context.moveTo(lastEvent.offsetX, lastEvent.offsetY);
  context.lineTo(e.offsetX, e.offsetY);
  context.stroke();
});

Following Gøran Smistad's proposed solution in (https://teamtreehouse.com/community/simple-drawing-application-pt-11) resolved 1st error. (I don't understand this either, as Andrew's code worked without setting value after declaring lastEvent. Is this just something that changed with time?)

But this 2nd error ("Uncaught ReferenceError: e is not defined") is not going away, and I am unable to find a resolution so far...

If anyone has any idea, please share...

Thanks in advance!

1 Answer

Grace Nellore
Grace Nellore
9,447 Points

Wow I looked at this line by line, and I still totally missed it! Sorry all, and I will keep this just in case anyone else has similar issue/for reference.

Original:

// On mouse events on the canvas
$canvas.mousedown(function(e){
  lastEvent = e;
}).mousemove(function(){ // missing e
  // Draw lines
  context.beginPath();
  context.moveTo(lastEvent.offsetX, lastEvent.offsetY);
  context.lineTo(e.offsetX, e.offsetY);
  context.stroke();
});

Working now:

// On mouse events on the canvas
$canvas.mousedown(function(e){
  lastEvent = e;
}).mousemove(function(e){ // e added
  // Draw lines
  context.beginPath();
  context.moveTo(lastEvent.offsetX, lastEvent.offsetY);
  context.lineTo(e.offsetX, e.offsetY);
  context.stroke();
});