JSFiddle - React, Tailwind, and code Playground

HTML

<div class="yo">
</div>

JavaScript

var thz_icon_source = {"Spinners":["spinnericon1","spinnericon2"],"Awesome":["awesomeicon1","awesomeicon2"]};
var fa_icon_source = {"Spinners":["faspinner1","faspinner2"],"Awesome":["faawesome1","faawesome2"]};

function mergeJSON(json1,json2)
{
    var result = json1 ;
    for (var prop in json2) 
    {
        if (json2.hasOwnProperty(prop)) 
        {
            result[prop] = result[prop].concat(json2[prop]);
        }
    }
    return result;
}


$(".yo").html(JSON.stringify(mergeJSON(thz_icon_source,fa_icon_source)));