Chart.js – Formatting Y axis

I had the same problem, I think in Chart.js 2.x.x the approach is slightly different like below.

ticks: {
    callback: function(label, index, labels) {
        return label/1000+'k';
    }
}

More in details

var options = {
    scales: {
        yAxes: [
            {
                ticks: {
                    callback: function(label, index, labels) {
                        return label/1000+'k';
                    }
                },
                scaleLabel: {
                    display: true,
                    labelString: '1k = 1000'
                }
            }
        ]
    }
}