Selection of polygon Using Arcgis Javascript

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Hello All,

I am having polygons drawn on map after using bufferparameters.Now my challenge is to use selection tool .When I try to select any one of the polygon I need to change the symbol of that polygon that it has been selected.

I am having my drawn extent and polygon extents with me.

I have to do this using Arcgis Javascript API

Please provide solution .

Thankyou
Aravind