Format Highcharts y-axis labels

Question

I'm using Highcharts to generate a line chart that shows currency values. By default the y-axis labels use metric prefixes for abbreviation, e.g. 3k is displayed instead of 3000

I would like to prepend a currency symbol to these labels, e.g. display $3k instead of 3k. However as soon as I add the currency symbol, the metric prefixes are no longer used. I've tried the following

    yAxis: {
        labels: {                
            formatter: function () {
                return '$' + this.value;
            }
        }
    }

and also tried

    yAxis: {
        labels: {
            format: '${value}'
        }
    }

But in both cases $3000 is displayed instead of $3k. Is it possible to add a currency symbol without losing the metric prefix?

Here's a demo (JSFiddle here) that illustrates the problem

$(function() {
  $('#container').highcharts({

    yAxis: {
      // if you include the lines below, the metric prefixes disappear
      /*
      labels: {
          format: '${value}'
      }
      */
    },

    series: [{
      data: [15000, 20000, 30000]
    }]

  });
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.2/jquery.min.js"></script>
<script src="https://code.highcharts.com/highcharts.js"></script>

<div id="container" style="height: 400px; width: 500px"></div>

Answer 1

You can call the original formatter from your formatter function:

$(function () {
    $('#container').highcharts({

        yAxis: {            
            labels: {
                formatter: function () {
                    return '$' + this.axis.defaultLabelFormatter.call(this);
                }            
            }
        },

        series: [{
            data: [15000, 20000, 30000]
        }]

    });
});

http://jsfiddle.net/x6b0onkp/2/

Answer 2

I looked in HighCharts source code and found out that if you pass a format or formatter it won't add numeric symbol. It is inside else if statement i.e. formatOption xor numericSymbol. So you need to add a formatter and do the logic yourself.

this is a slightly modified copy-paste of their code:

       formatter: function() {
           var ret,
               numericSymbols = ['k', 'M', 'G', 'T', 'P', 'E'],
               i = numericSymbols.length;
           if(this.value >=1000) {
               while (i-- && ret === undefined) {
                   multi = Math.pow(1000, i + 1);
                   if (this.value >= multi && numericSymbols[i] !== null) {
                      ret = (this.value / multi) + numericSymbols[i];
                   }
               }
           }
           return '$' + (ret ? ret : this.value);
       }

http://jsfiddle.net/x6b0onkp/1/