Chart.js axes label font size

In chart.js how can I set the set the font size for just the x axis labels without touching global config?

I've already tried setting the 'scaleFontSize' option my options object. I've also tried setting:

{
  ...
  scales: {
    xAxes: [{
      scaleFontSize: 40
      ...
    }]
   }
}

The fontSize attribute is actually in scales.xAxes.ticks and not in scales.xAxes as you thought.

So you just have to edit the attribute like this :

var options = {
    scales: {
        yAxes: [{
            ticks: {
                fontSize: 40
            }
        }]
    }
}

Configuration options and properties for chartjs 3.0 has changed. Currently I'm using Chartjs 3.1.1. Fonts are used as objects now. In order to change font size of x axis ticks you have to use following configuration.

var options = {
    scales: {
        x: {
            ticks: {
                font: {
                    size: 12,
                }
            }
        }
    }
};

Checkout this jsfiddle sample.

Try this is working

     options: {
        scales: {
           xAxes: [{
                   ticks: {
                    fontSize: 10
                   }
                  }]
                }
             }

Try to see if this will work

{
  ...
  scales: {
    xAxes: [{
      fontSize: 40
      ...
    }]
   }
}

It doesn't look like scaleFontSize is a valid property.

options: {
                  locale: 'fa-IR',
                  responsive: true, // Instruct chart js to respond nicely.
                  maintainAspectRatio: false, // Add to prevent default behaviour of full-width/height 
                        plugins: {
                          legend: {
                              position: 'top',
                              labels: {
                                  font: {
                                    size: 9,
                                    family:'vazir'
                                  }
                             }
                          },
                          title: {
                            display: true,
                            text: chart_info.chartTitle,
                            font: {
                                size: 16,
                                family:'vazir'
                            }
                          },
                          tooltip: {
                              bodyFont: {
                                size: 13,
                                family:'vazir'
                              }
                         }
                    },
                    scales: {
                        x: {
                            ticks: {
                                font: {
                                    size: 10,
                                    family:'vazir'
                                }
                            }
                        },
                        y: {
                            ticks: {
                                font: {
                                    size: 10,
                                    family:'vazir'
                                }
                            }
                        }                       
                    }
                }