Component definition

ko.components.register('progress-bar', {
    viewModel: function(params) {
            var that = this;
    
        // progress is a numeric value between 0 and 100
        that.progress = params.progress;
        
        
        that.progressPercentual = ko.computed(function(){
            return '' + ko.utils.unwrapObservable(that.progress) + '%';
        })
    },
    template:
        '<div class="progress"> <div data-bind="attr:{\'aria-valuenow\':progress}, style:{width:progressPercentual}, text:progressPercentual" class="progress-bar" role="progressbar" aria-valuenow="0" aria-valuemin="0" aria-valuemax="100" style="min-width: 2em;"></div> </div>'
});

Html usage

<progress-bar params="progress:5"></progress-bar>