Check a radio button with javascript
Do not mix CSS/JQuery syntax (# for identifier) with native JS.
Native JS solution:
document.getElementById("_1234").checked = true;
JQuery solution:
$("#_1234").prop("checked", true);
If you want to set the "1234" button, you need to use its "id":
document.getElementById("_1234").checked = true;When you're using the browser API ("getElementById"), you don't use selector syntax; you just pass the actual "id" value you're looking for. You use selector syntax with jQuery or .querySelector() and .querySelectorAll().
Today, in the year 2016, it is save to use document.querySelector without knowing the ID (especially if you have more than 2 radio buttons):
document.querySelector("input[name=main-categories]:checked").value