With which halogen acid peroxide effect or Kharasch effect is possible

H – Cl bond is stronger (430 KJ mol^-1) than H – Br bond (364 KJ mol^-1). So not cleaved easily. H – I bond is weak (297 KJ mol^-1) cleaved easily. But the formed . I free radicals readily combine to form Iodine instead of adding to the double bond.