Customizing default y-axis label in Highcharts - highcharts

Question

I want to prefix a $ to the default y-axis label. My bar chart is using values in the millions so the chart is returning value-MM (80MM, 30MM). What I would like to do is format the y-axis like $-value-MM ($80MMm $30MM). I have tried the code below and can't get it to work?
yAxis: [{ // Primary yAxis
labels: {
formatter: function () {
return '$' + this.value;
}
},
title: {
text: 'Revenue',

Answer 1

If I understand the question correctly, your data already has 'MM' suffix and you want to add the prefix '$'.
Try,
yAxis: {
labels: {
format: '${value}'
}
}

Answer 2

One rather elaborate way to achieve this is to re-use the code Highcharts uses in their internal defaultLabelFormatter for axis that are numeric, and use it in the axis formatter.
An example of this, with your added prefix (JSFiddle):
yAxis: {
labels: {
formatter: function() {
var numericSymbols = Highcharts.getOptions().lang.numericSymbols;
var i = numericSymbols && numericSymbols.length;
var numericSymbolDetector = this.axis.isLog ? this.value : this.axis.tickInterval;
var UNDEFINED, ret, multi;
while (i-- && ret === UNDEFINED) {
multi = Math.pow(1000, i + 1);
if (numericSymbolDetector >= multi && (this.value * 10) % multi === 0 && numericSymbols[i] !== null) {
ret = Highcharts.numberFormat(this.value / multi, -1) + numericSymbols[i];
}
}
if (ret === UNDEFINED) {
if (Math.abs(this.value) >= 10000) {
ret = Highcharts.numberFormat(this.value, -1);
} else {
ret = Highcharts.numberFormat(this.value, -1, UNDEFINED, '');
}
}
return "$"+ret; // Adding the prefix
}
},
}
A experimental short form of this would be to call the defaultLabelFormatter with the essential parts of the context it requires. An example of this (JSFiddle):
yAxis: {
labels: {
formatter: function() {
return "$" + this.axis.defaultLabelFormatter.call({
axis: this.axis,
value: this.value
});
}
},
}
As the context is incomplete it wouldn't work as expected if your axis was datetime or categories or perhaps logarithmical, but should work for numeric axis. For the full picture I suggest looking at the full defaultLabelFormatter implementation.