Set value within json postgresql 9.4

I have the following problem: I need to do an update within json with the aim of changing " typedata " to a new value that is given to me.

{ "nametable":"venta",
  "data":"name":"1",
  "cols":"Tienda":"typedata":"varchar"
},
  "Fecha":"typedata":"date"},  
  "Region":"typedata":"varchar"
  }
 }
},
"name":"2","cols":"Precio":"typedata":"numeric"
},
"Costounico":"typedata":"numeric"
},
"Cantidad":{"typedata":"numeric"}}}]}'

I would appreciate help on this topic.