highcharts tooltip format millions billions

Question

I want to display couple of points on a highcharts line chart which are big numbers.

e.g. 100,000, 10,000,000, 1,000,000,000

When I display these, the y axi

Answer 1

You can use the same logic as implemented in Highcharts core:

    tooltip: {
        formatter: function () {
            var ret = '',
                multi,
                axis = this.series.yAxis,
                numericSymbols = ['k', 'M', 'G', 'T', 'P', 'E'],
                i = numericSymbols.length;
            while (i-- && ret === '') {
                multi = Math.pow(1000, i + 1);
                if (axis.tickInterval >= multi && numericSymbols[i] !== null) {
                    ret = Highcharts.numberFormat(this.y / multi, -1) + numericSymbols[i];
                }
            }
            return ret;
        }
    },

And jsFiddle: http://jsfiddle.net/ynCKW/2/

EDIT for Highcharts v6:

We can call build-in method, which should be easier to maintain: http://jsfiddle.net/BlackLabel/ynCKW/104/

    tooltip: {
        valueSuffix: '',
        formatter: function () {
            var axis = this.series.yAxis;

            return axis.defaultLabelFormatter.call({
                axis: axis,
                value: this.y
            });
        }
    },

Answer 2

Piggybacking off @Pawel Fus, a slight tweak allows you to have negative currency values as well but with the negative outside the $ (i.e. -$100K versus -$-100k).

function () {
    var isNegative = this.value < 0 ? '-' : '';
    var absValue = Math.abs(this.value);
    return isNegative + '$' + this.axis.defaultLabelFormatter.call({
        axis: this.axis,
        value: absValue
    });
}

Here is a jsFiddle: http://jsfiddle.net/4yuo9mww/1/