chart instance has properties "ctx", "canvas", "chartArea"

ctx, canvas
https://github.com/chartjs/Chart.js/blob/master/src/core/core.controller.js#L78-L79

chartArea
https://github.com/chartjs/Chart.js/blob/master/src/core/core.layoutService.js#L417-L423

types/chart.js/chart.js-tests.ts

@@ -26,3 +26,12 @@ let chart: Chart = new Chart(new CanvasRenderingContext2D(), {
     }
 });
 chart.update();
+
+console.log(chart.ctx && chart.ctx.font);
+console.log(chart.canvas && chart.canvas.tagName);
+if (chart.chartArea) {
+    console.log(chart.chartArea.top);
+    console.log(chart.chartArea.right);
+    console.log(chart.chartArea.bottom);
+    console.log(chart.chartArea.left);
+}

types/chart.js/index.d.ts

@@ -26,6 +26,9 @@ declare class Chart {
     getElementAtEvent: (e: any) => {};
     getElementsAtEvent: (e: any) => Array<{}>;
     getDatasetAtEvent: (e: any) => Array<{}>;
+    ctx: CanvasRenderingContext2D|null;
+    canvas: HTMLCanvasElement|null;
+    chartArea: Chart.ChartArea;
     static pluginService: PluginServiceStatic;
 
     static defaults: {
@@ -80,6 +83,13 @@ declare namespace Chart {
 
     type PositionType = 'left' | 'right' | 'top' | 'bottom';
 
+    interface ChartArea {
+        top: number;
+        right: number;
+        bottom: number;
+        left: number;
+    }
+
     interface ChartLegendItem {
         text?: string;
         fillStyle?: string;