Trigger keydown on text-input with jQuery, retain value after event

Question

Using Tampermonkey on an angularjs site. I'm prepopulating an inputbox with a value whenever I open the url, but the search is triggered by typing. So I need a keydown-event ie "space" to trigger the search.

I've figured out how to trigger a keydown-event, but it overrides the value already in the inputbox. How do I retain it, while still triggering a keydown?

(function() {
'use strict';

var herId = getParameterByName('Q');
window.setTimeout(function() {
    var el = document.querySelector('.form-control');
    el.value = herId;
}, 200);

window.setTimeout(function() {
    var e = jQuery.Event("keydown");
    e.which = 32; // # Some key code value
    $("input").val(String.fromCharCode(e.which));
    $("input").trigger(e);
}, 1600);
})();

function getParameterByName(name, url) {
   if (!url) url = window.location.href;
   name = name.replace(/[\[\]]/g, "\\$&");
   var regex = new RegExp("[?&]" + name + "(=([^&#]*)|&|#|$)"),
   results = regex.exec(url);
   if (!results) return null;
   if (!results[2]) return '';
   return decodeURIComponent(results[2].replace(/\+/g, " "));
}

I'm using the delays because the page takes some time to load.

Answer 1

Every time the keydown event runs, the old value is cleared out and replace by the new String.fromCharCode character.

//Try this
(function() {
'use strict';

var herId = getParameterByName('Q');
window.setTimeout(function() {
    var el = document.querySelector('.form-control');
    el.value = herId;
}, 200);

window.setTimeout(function() {
    var e = jQuery.Event("keydown");
    e.which = 32; // # Some key code value

    $("input").val($(this).val() + String.fromCharCode(e.which));
    $("input").trigger(e);
}, 1600);
})();

function getParameterByName(name, url) {
   if (!url) url = window.location.href;
   name = name.replace(/[\[\]]/g, "\\$&");
   var regex = new RegExp("[?&]" + name + "(=([^&#]*)|&|#|$)"),
   results = regex.exec(url);
   if (!results) return null;
   if (!results[2]) return '';
   return decodeURIComponent(results[2].replace(/\+/g, " "));
}