A ChartJs plugin to add offset to chart's min/max on the y axes

README.md

A ChartJs plugin to add offset to chart's min/max on the y axes

Take a look at this SF question for more details, see my answer.

how to use:

1. Add code after chartjs code
2. In chartsjs options set options.customOffset to any number you want to offset the chart

chartjs-plugin-yoffset.js

// based on my answer here: https://stackoverflow.com/questions/47146427
Chart.pluginService.register({
    beforeUpdate: function(chart){
      // get custom defined offset
      var offset = chart.options.customOffset;
      // exisit gracefully if offset not defined or less than 0
      if(!offset || offset < 0) return;
      var yAxes = chart.options.scales.yAxes;
      for(var i=0; i<yAxes.length; i++){
        var axis = yAxes[i];
        var datasets = chart.data.datasets;
        var max = Number.MIN_VALUE;
        var min = Number.MAX_VALUE;
        var datasetsOnAxis = [];

        for(var j=0; j<datasets.length; j++){ // add datasets for this axes to datasetsOnAxis
          var dataset = datasets[j];
          var meta = chart.getDatasetMeta(j);
          if  (meta.yAxisID === axis.id) datasetsOnAxis.push(dataset); 
        }

        for(var k=0; k<datasetsOnAxis.length; k++){
          var dataset = datasetsOnAxis[k]
          var newMax = Math.max.apply(null, dataset.data);
          var newMin = Math.min.apply(null, dataset.data);
          max = newMax > max ? newMax : max;
          min = newMin > min ? min : newMin;
        }
        axis.ticks.max = max + offset;
        axis.ticks.min = min - offset;   
      }
    }
});