How to enable unique permissions for a List object via JSOM

Use SP.SecurableObject.hasUniqueRoleAssignments property to determine whether the role assignments are uniquely defined for a List or inherited from a parent securable object.

Use SP.SecurableObject.breakRoleInheritance(copyRoleAssignments, clearSubscopes) Method to set unique role assignments for the List object.

Example

var listTitle = 'Documents';

var context = SP.ClientContext.get_current();

var list = context.get_web().get_lists().getByTitle(listTitle);   



context.load(list,'HasUniqueRoleAssignments'); 

context.executeQueryAsync(

   function(){

      var hasUniqueAssgns = list.get_hasUniqueRoleAssignments();

      if(!hasUniqueAssgns) {

         list.breakRoleInheritance(false, true);

         context.executeQueryAsync(

            function(){

                console.log('Success');

            }, 

            function(sender,args){

               console.log(args.get_message());    

            }

         );

      }

   }, 

   function(sender,args){

      console.log(args.get_message());    

   }

);

How to grant custom permissions for a List object via JSOM

The following example demonstrates how to break role inheritance for a List object and grant Full Control permissions for a current user

Example

var listTitle = 'Documents';

var context = SP.ClientContext.get_current();

var list = context.get_web().get_lists().getByTitle(listTitle);   

var currentUser = context.get_web().get_currentUser();



list.breakRoleInheritance(false, true); // break role inheritance first!



var roleDefBindingColl = SP.RoleDefinitionBindingCollection.newObject(context);

roleDefBindingColl.add(context.get_web().get_roleDefinitions().getByType(SP.RoleType.administrator));

list.get_roleAssignments().add(currentUser, roleDefBindingColl);



context.executeQueryAsync(

   function(){

      console.log('Success');

   }, 

   function(sender,args){

      console.log(args.get_message());    

   }

);