finding area,perimeter by coordinates

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Javascript

we input the points like (xi,yi), depending on number of points it has to caluclate area,permeter.
if i give two points it is line,if three points it is triangle,if 4 it is quadrilateral.
if one point&radius it caluclate circle area,permeter.
if we provide irrelevent data it has to give some alert message.
irrelevent data means istead of giving points if we give an other data like characters,numbers i.e:wrong input