Finding map extent for javascript api and spatial reference

[yockee]

I am having trouble in finding map extent (bounding box). How can I easily find out the extent and its format ?

Suppose I have this code sample:

const view = new MapView({
container: "viewDiv",
map: map,

extent: {
// autocasts as new Extent()
xmin: -9177811,
ymin: 4247000,
xmax: -9176791,
ymax: 4247784,
spatialReference: 102100

I want to direct the extent (xmin/max, ymin/max) to a particular city with spatial reference 102100. How to do that ?

And also, spatialReference 102100 (line 11) is deprecated and changed to EPSG 3857. (https://spatialreference.org/ref/esri/102100/) . Do I have to change the "spatialReference: 102100" to "spatialReference: 3857" ?

Thanks