Chartjs2 Legend Not working - ajax

Question

I'm trying to plot a lineal graphic that gets data from ajax using Chartjs 2.5.
This is the main function for this procedure. The main problem is that the legend doesn't appear.
function initDigitalValueChart(divName, ids) {
if ($(divName)) {
/*for (var j=0; j<ids.length; j++) {
console.log(j);
datasetValue[j] = {
fillColor: 'rgba(220,220,220,0.5)',
strokeColor :'rgba(220,220,220,1)',
title :'2013',
data : [Math.round(Math.random() * 1),Math.round(Math.random() * 1)]
}
}*/
var datasetValue = [];
var calls = [];
for (var j = 0; j < ids.length; j++) {
var labels = []
URL = "*****" + ids[j];
calls.push($.getJSON(URL, function(response) {
var values = []
if (response != null) {
$.each(response, function(index, data) {
labels.push(data["timestamp"]);
values.push(data["value"]);
title = data["sensorName"]
});
datasetValue.push({
label: title,
lineTension: 0,
borderColor: "rgba(" + Math.floor(Math.random() * 255) + ", " + Math.floor(Math.random() * 255) + ", " + Math.floor(Math.random() * 255) + ", 0.70)",
backgroundColor: "transparent",
data: values,
radius: 0,
pointHitRadius: 0,
steppedLine: true,
});
}
}))
}
$.when.apply($, calls).then(function() {
var ctx = document.getElementById('digital').getContext("2d");
var lineChart = new Chart(ctx, {
type: 'line',
data: {
labels: labels,
datasets: datasetValue
},
options: {
legend: {
display: true,
labels: {
fontColor: "white",
fontSize: 18
}
},
scales: {
xAxes: [{
display: true,
scaleLabel: {
display: true,
labelString: 'Data Hora'
}
}],
yAxes: [{
display: true,
scaleLabel: {
display: true,
labelString: 'Valor'
}
}]
}
}
});
//document.getElementById('digital-legend').innerHTML = lineChart.generateLegend();
});
}
}
I tried to add the position: 'top' option but in this case the console returns
Uncaught TypeError: Cannot read property 'call' of undefined
Has anyone else had problems with this?