JSFiddle - React, Tailwind, and code Playground

HTML

<span data-bind="text: paddedProjectId"></span>

JavaScript

var vm = { ProjectId: 5 }
    
    vm.paddedProjectId = ko.computed(function() {
        return vm.ProjectId < 10 ? '0' + vm.ProjectId.toString() : vm.ProjectId;
    });
                                 

ko.applyBindings(vm);