未捕获的TypeError:无法读取未定义的属性“数据集”

I'm trying to use Chart.js in my program. I have hosted my php and JavaScript files in a public hosting site. When I try to run the chart function, I'm getting the following error:

Uncaught TypeError: Cannot read property 'datasets' of undefined". Please find the code below.

<head>
    <title>Operation Details</title>
    <script src="../Chart.js"></script>
</head>
var barChartData = { 
    labels : [month1,month2,month3,month4,month5,month6,month7,month8,month9,month10,month11,month12],
    datasets : [ 
        { 
        label: "My First dataset", fillColor : "rgba(192,192,192,0.5)", strokeColor : "rgba(192,192,192,0.8)", highlightFill: "rgba(192,192,192,0.75)", highlightStroke: "rgba(192,192,192,1)",
        data : [avg1[temp[i]],avg2[temp[i]]]
        }
    ]
}
//...

window.onload = function(){
    var ctx = document.getElementById("canvas").getContext("2d");
    window.myBar = new Chart(ctx).Bar(barChartData, {
        responsive: true
    });
//...
}

Chart.js:

helpers.each(data.datasets,function(dataset,datasetIndex){

    var datasetObject = {
    //...

I'm completely new to JavaScript and to this forum. If something is wrong, please advice me on that.