JSFiddle - React, Tailwind, and code Playground

HTML

What is array? Where is it defined?

What is load? Where is it defined?
What is j? Where is it defined?
What is list_left? Where is it defined?

JavaScript

var i;
var j;
var list_left;
var list_right;
var array;
$(document).ready(function() {
    $.getJSON("/getAliasForMatchAll/",
        function (data){
            array = data.aliases_id;
            load(array);
        });
    $("#next_left").click(next_left);

    //load(array_with_alias_id);
});
function load(data){
    list_left = new Array(data.length);
    list_right = new Array(data.length);
    for (alias in data){
        list_left[alias] = data[alias].id;
        list_right[alias] = data[alias].id;
    }
    i = -1;
    j = -1;

}


function next_left(){
    if(j >= array.length-1){
        var l = j
    } else {
        var l = j+=1;
    }
    
    $("#alias_id_left").val(list_left[l]);
    $("#merge_alias_id_left").val(list_left[l]);
    $.post("/visor/",{"alias_id":list_left[l],"position":"L"},
            function(data){
                $("#tabsL").html(data).ready(function(){
                    $("#tabsL").tabs();
                });
            });
}