How to set previous button is show after next button is click

this is my js code**

frappe.pages[‘subject’].on_page_load = function(wrapper) {
frappe.subject = new frappe.Subject(wrapper);
frappe.breadcrumbs.add(“subject”, “Student Test”);
}

frappe.Subject = Class.extend({
init: function(parent) {
this.parent = parent;
this.make();
this.refresh();
},
refresh: function() {
//if(!this.student_test)
{
this.show_start();
}
},
make: function() {
this.page = frappe.ui.make_app_page({
parent: this.parent,
title: __(“Test”),
single_column: true
});

},
show_start: function() {
    this.page.main.html(frappe.render_template("student_test_builder_start", {}));
    this.page.clear_actions();
    this.page.set_title(__("Test"));
    this.start_question();
    this.start_answare();
},
start_question: function() {
    // Test control
    var me = this;
    this.question_input = frappe.ui.form.make_control({
        parent: this.page.main.find(".question"),
        df: {
            fieldtype: "Read Only",
        
            label: __("Que"),
        },
        render_input: true
    });

},
start_answare: function() {
    var me = this;
    this.answare_input = frappe.ui.form.make_control({
        parent: this.page.main.find(".answare"),
        df: {
            fieldtype: "Small Text",

            label: __("Ans")
        },
        render_input: true
    });
    
},        

});

this is my html code

<button class="btn btn-sm btn-default btn-previos-question">
        {%= __("<< Previous") %}</button>
    <button class="btn btn-sm btn-default btn-next-question">
        {%= __("Next >>") %}</button>
</p>

You can use jquery (?)

no
but why?

please sir give me reply this question…

@pankaj sorry not able to understand.