ZoomIn ZoomOut in Fabric.js

https://groups.google.com/forum/?fromgroups#!topic/fabricjs/WQ0jegaIFCY

by duckywang1

HTML

<script src="https://raw.github.com/kangax/fabric.js/master/dist/all.js"></script>
<script src="https://cdn.bootcss.com/fabric.js/2.2.0/fabric.js"></script>
<button id="btnZoomIn">ZoomIn</button> <button id="btnZoomOut">ZoomOut</button> <button id="btnResetZoom">Reset Zoom</button>
<br/>
<canvas id="c" width="400" height="400"></canvas>

CSS

canvas{
  border-width: 1pz;
  border-style: solid;
  border-color: #000;
}

JavaScript

var src = "http://fabricjs.com/lib/pug.jpg";
var copiedObject;
var copiedObjects = new Array();
var canvasScale = 1;
var SCALE_FACTOR = 1.2;

// canvas
var canvas = new fabric.Canvas('c');
canvas.backgroundColor = "#F5F5F5";

// text
var text = new fabric.Text('Text inside canvas', { 
  left: 200, 
  top: 50 
});
text.hasRotatingPoint = true;
canvas.add(text);

// circle
var circle = new fabric.Circle({
    left: 200,
    top: 150,
    radius: 50,
    fill: "#dd0000"
});
circle.hasRotatingPoint = true;
canvas.add(circle);

//image
fabric.util.loadImage(src, function(img) {
    var object = new fabric.Image(img);
    object.set({ 
        left: 200, 
        top: 300
    });
    object.hasRotatingPoint = true;
    object.scaleX = object.scaleY = .25;
    canvas.add(object);
    canvas.renderAll();    
});

canvas.renderAll();


// button Zoom In
$("#btnZoomIn").click(function(){
    zoomIn();
});
// button Zoom Out
$("#btnZoomOut").click(function(){
    zoomOut();
});
// button Reset Zoom
$("#btnResetZoom").click(function(){
    resetZoom();
});

createListenersKeyboard();

function createListenersKeyboard() {
    document.onkeydown = onKeyDownHandler;
    //document.onkeyup = onKeyUpHandler;
}

function onKeyDownHandler(event) {
    //event.preventDefault();
    
    var key;
    if(window.event){
        key = window.event.keyCode;
    }
    else{
        key = event.keyCode;
    }
    
    switch(key){
        //////////////
        // Shortcuts
        //////////////
        // Zoom In (Ctrl+"+")
        case 187: // Ctrl+"+"
            if(ableToShortcut()){
                if(event.ctrlKey){
                    event.preventDefault();
                    zoomIn();
                }
            }
            break;    
        // Zoom Out (Ctrl+"-")
        case 189: // Ctrl+"-"
            if(ableToShortcut()){
                if(event.ctrlKey){
                    event.preventDefault();
                    zoomOut();
                }
            }
       ...