amCharts - XY Charts Tooltip and Bullet - amcharts

Question

I have an XY Charts in amCharts 4 and I can't set the correct parameter to insert in the tooltip. This is the code that design the chart:
Is possible to show the parameter "desc" in the tooltip?
var chart = am4core.create("chartdiv", am4charts.XYChart);
// Add data
chart.data = [ {
"x": -6,
"y": 0,
"diam": 4,
"desc": "test"
}, {
"x": 0,
"y": -10,
"diam": 4,
"desc": "test"
}, {
"x": 12,
"y": 10,
"diam": 8,
"desc": "special"
} ];
// Create axes
var xAxis = chart.xAxes.push(new am4charts.ValueAxis());
var yAxis = chart.yAxes.push(new am4charts.ValueAxis());
// Create series
var series = chart.series.push(new am4charts.LineSeries());
series.dataFields.valueX = "x";
series.dataFields.valueY = "y";
series.strokeWidth = 2;
series.fillOpacity = 0;
series.stroke = "red";
// Create bullet and tooltip
seriesBullet = series.bullets.push(new am4charts.CircleBullet());
seriesBullet.circle.fill = am4core.color("#fff");
seriesBullet.circle.strokeWidth = 3;
seriesBullet.circle.propertyFields.radius = "diam";
seriesBullet.tooltipText = "desc";
#chartdiv {
width: 100%;
height: 200px;
}
<script src="https://www.amcharts.com/lib/4/core.js"></script>
<script src="https://www.amcharts.com/lib/4/charts.js"></script>
<div id="chartdiv"></div>

Answer 1

You need to wrap the desc in curly braces: {desc}
seriesBullet.tooltipText = "{desc}";
Here is your updated working example:
var chart = am4core.create("chartdiv", am4charts.XYChart);
// Add data
chart.data = [ {
"x": -6,
"y": 0,
"diam": 4,
"desc": "test"
}, {
"x": 0,
"y": -10,
"diam": 4,
"desc": "test"
}, {
"x": 12,
"y": 10,
"diam": 8,
"desc": "special"
} ];
// Create axes
var xAxis = chart.xAxes.push(new am4charts.ValueAxis());
var yAxis = chart.yAxes.push(new am4charts.ValueAxis());
// Create series
var series = chart.series.push(new am4charts.LineSeries());
series.dataFields.valueX = "x";
series.dataFields.valueY = "y";
series.strokeWidth = 2;
series.fillOpacity = 0;
series.stroke = "red";
series.tooltipText = "{desc}";
// Create bullet and tooltip
seriesBullet = series.bullets.push(new am4charts.CircleBullet());
seriesBullet.circle.fill = am4core.color("#fff");
seriesBullet.circle.strokeWidth = 3;
seriesBullet.circle.propertyFields.radius = "diam";
seriesBullet.tooltipText = "{desc}";
#chartdiv {
width: 100%;
height: 200px;
}
<script src="https://www.amcharts.com/lib/4/core.js"></script>
<script src="https://www.amcharts.com/lib/4/charts.js"></script>
<div id="chartdiv"></div>

Answer 2

You need to put your parameter inside a {} curly braces.
E.g :
seriesBullet.tooltipText = "{desc}";