let width, height, gradient;functiongetGradient(ctx, chartArea){const chartWidth = chartArea.right - chartArea.left;const chartHeight = chartArea.bottom - chartArea.top;if(!gradient || width !== chartWidth || height !== chartHeight){// Create the gradient because this is either the first render// or the size of the chart has changed
width = chartWidth;
height = chartHeight;
gradient = ctx.createLinearGradient(0, chartArea.bottom,0, chartArea.top);
gradient.addColorStop(0, Utils.CHART_COLORS.blue);
gradient.addColorStop(0.5, Utils.CHART_COLORS.yellow);
gradient.addColorStop(1, Utils.CHART_COLORS.red);}return gradient;}