How are the values in the vue child component submitted to the parent component for AJAX to request different data?

I am a novice, expecting VUER to give me the strength to move forward. I encountered a problem. I couldn"t find out many solutions for two days.
this is the sub-component code I wrote:

Vue.component("list-ol",{
    props:["name_en","name_cn"],
    created:function(){
    },
    template:`
        <li class="li-catalog pull-left">{{ name_cn }} {{ name_en }}
        <span v-on:click="$emit("pronouce", name_en)" class="glyphicon glyphicon glyphicon-headphones headphone-icon"></span></li>
             `
});

var app = new Vue({
    el:"-sharpapp",
    data:{
        catalogList:[],
        level:""
    },
    created: function(){
            this.getCatalogList();
            this.levelHandler();
    },
    methods:{
        // word$emit
        // vm.$emit( eventName, [args] )
        // :
        // {string} eventName
        // [...args]
        // 

        pronouce:function(word){
            pronouceIt(word);

        },
        levelHandler:function(level){
            //Vue.set(this,"level",lvl);
            //alert(level);
        },
        getCatalogList:function(event){
            var componentObj = this;//In case of "this" will be pointed to Jquery object
            //:JQUERYAJAXJSONVUE
            $.getJSON("getcataloglist.php", {act: "fetchcatalog",level:"1"}, function(json, textStatus) {
                Vue.set(componentObj,"catalogList",json);
            });
        }
    }

});

this is HTML"s COMPONENT:

           <level-tip **level="1"**></level-tip>
            <ol>
                <list-ol v-on:pronouce="pronouce"
                        v-on:levelHandler ="levelHandler"
                        v-for="item in catalogList"
                        v-bind:key="item.Id"
                        v-bind:name_en="item.name_en"
                        v-bind:name_cn="item.name_cn"
                        >
                </list-ol>

The level=1 in

means that if I want to reuse this COMPONENT, I just need to change the level=2, in it and pass this value to $.getJSON to get different data blocks, so that I can display different contents in the list-ol. (this level=1 should be better placed in the list-ol component? )
asked a lot of questions at once. I don"t know if my question is clear. Thank you

Php vue.js

May.22,2021

How are the values in the vue child component submitted to the parent component for AJAX to request different data?

the first question JSON is sent to VUE

the second question is where to put level=1