JSFiddle - React, Tailwind, and code Playground

JavaScript

a = {"first":[1, 2, 3, 4], "second":[1, 2, 3, 4]}

b = a;
$("body").append("B: {<br/>");
for (property in b) {
    $("body").append("&nbsp;"+property+" : ["+b[property]+"], <br/>");
}
$("body").append("}<br/>---------delete from A---------<br/>B: {<br/>");
delete a.second;

for (property in b) {
    $("body").append("&nbsp;"+property+" : ["+b[property]+"], <br/>");
}
$("body").append("}");