javascript - Knockout.js custom validation rule for logical OR for two input fields -

how can validate 2 input fields knockout.js? rule is: @ least 1 of input fields must filled in.

ko.validation.rules['or'] = {     validator: function (val, otherval) {         return (val || otherval);     },     message: "you have fill in @ least 1 of 2 input fields!" };  ko.validation.registerextenders();   self.description = ko.observable().extend({ or:  self.title }); self.title = ko.observable().extend({ or:  self.description }); 

at moment: on init 1 of fields red , 1 green - should both red on start.

https://github.com/knockout-contrib/knockout-validation

 self.title = ko.observable().extend({ or:  self.description });  self.description = ko.observable().extend({ or:  self.title }); 

title valid description not valid on start. when change code order to:

self.description = ko.observable().extend({ or:  self.title });       self.title = ko.observable().extend({ or:  self.description }); 

then opposite.

even example knockout contribution doesn't work me: https://github.com/knockout-contrib/knockout-validation/wiki/user-contributed-rules

ko.validation.rules['requiresoneof'] = {   getvalue: function (o) {     return (typeof o === 'function' ? o() : o);   },   validator: function (val, fields) {     var self = this;      var = ko.utils.arrayfirst(fields, function (field) {       var stringtrimregex = /^\s+|\s+$/g,                 testval;        var val = self.getvalue(field);        if (val === undefined || val === null)          return !required;        testval = val;       if (typeof (val) == "string") {         testval = val.replace(stringtrimregex, '');       }        return ((testval + '').length > 0);      });      return (anyone != null);   },   message: 'one of these fields required'  }; self.title = ko.observable(); self.description = ko.observable();   self.title.extend({requiresoneof: [self.title, self.description]}); self.description.extend({requiresoneof: [self.title, self.description]}); 

i found error. chicken-egg-problem.

at moment when gave title or description validation, not initialized yet. changed code , works:

//define validation rule: ko.validation.rules['or'] = {     validator: function (val, params) {         "use strict";         return (val !== "" && val !== undefined) || ( params.other() !== "" && params.other() !== undefined);     },     message: "you have fill in @ least 1 of 2 input fields!" };  ko.validation.registerextenders();   //apply validation rule:  self= this;      self.description = ko.observable();     self.title = ko.observable();      self.title.extend({         or: {             params: {other: self.description},             message: "please fill @ least 1 field!"         }     });      self.description.extend({         or: {             params: {other: self.title},             message: "please fill @ least 1 field!"         }});