To Check current users permissions using Ecmascript\Javascript client object model SharePoint 2010.

function checkifUserHasEditPermissions()

{

context = new SP.ClientContext.get_current();

web = context.get_web();

this._currentUser = web.get_currentUser();

context.load(this._currentUser);

context.load(web,'EffectiveBasePermissions');

context.executeQueryAsync(Function.createDelegate(this, this.onSuccessMethod), Function.createDelegate(this, this.onFailureMethod));

}

function onSuccessMethod(sender, args)

{

if (web.get_effectiveBasePermissions().has(SP.PermissionKind.editListItems))

{

//User Has Edit Permissions

}

}}