Viewport is the visible range of the axis and viewportMaximum allows you to set its maximum value. This can be used in combination with viewportMinimum in order to zoom into a certain region programmatically.
Default: Automatically Calculated based on the data  
Example: -100, 350..
 
   - viewportMinimum and viewportMaximum are useful in setting the initial zoom in a chart.
   
- If viewportMinimum and viewportMaximum are not set, minimum and maximum values of axis will become the viewport’s range.
   
- Setting viewportMinimum or viewportMaximum will make the zoom/pan toolBar visible. Clicking the reset button will set the viewport range to viewportMinimum and viewportMaximum.
   
- Setting viewportMinimum and viewportMaximum of all axis to null will hide the toolBar – equivalent to clicking reset button.
   
var  chart =  new  CanvasJS.Chart("container",
{
 .
 .
 axisX:{
   viewportMinimum: -50,
   viewportMaximum: 50
 },
 .
 . 
});
chart.render();
 
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