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JavaScript jQuery Basics (2014) Creating a Simple Drawing Application Perform: Part 5

Posted by Sauli Laitinen
Sauli Laitinen
5,992 Points

Is there an alternative way to "chaining"?

Hi,

In this exercise many things are chained(?) together. What I mean that the mosuedown is followed with mousemove, mouseup and mouseleave all in one line or statement.

I was wondering that would there have been an alternative way of writing all of this? I mean that could the mousedown, mousemove, mouseup and mouseleave have been separated to separate statements?

$canvas.mousedown(function(e){
  lastEvent = e;
  mouseDown = true;
}).mousemove(function(e){
    if(mouseDown === true) {
    context.beginPath();
    context.moveTo(lastEvent.offsetX, lastEvent.offsetY);
    context.lineTo(e.offsetX, e.offsetY);
    context.strokeStyle = color;
    context.stroke();
    lastEvent = e;
  }
}).mouseup(function(){
  mouseDown = false;
}).mouseleave(function(){
  $canvas.mouseup();
});

3 Answers

Ryan Boone
Ryan Boone
26,518 Points

Yes, you would just split out the mouse events and begin each command with $canvas, like so:

$canvas.mousedown(function(e){
  lastEvent = e;
  mouseDown = true;
});
$canvas.mousemove(function(e){
    if(mouseDown === true) {
    context.beginPath();
    context.moveTo(lastEvent.offsetX, lastEvent.offsetY);
    context.lineTo(e.offsetX, e.offsetY);
    context.strokeStyle = color;
    context.stroke();
    lastEvent = e;
  }
});
$canvas.mouseup(function(){
  mouseDown = false;
});
$canvas.mouseleave(function(){
  $canvas.mouseup();
});
Samuel Rueby
Samuel Rueby
22,538 Points

Yup, chaining can be beneficial but it's not required.

Steven Walters
Steven Walters
10,573 Points
Steven Walters
Steven Walters
10,573 Points

Doesn't it make sense to chain in this case because it's all one action.

Sauli Laitinen
Sauli Laitinen
5,992 Points
Sauli Laitinen
Sauli Laitinen
5,992 Points

Ok, thanks.