Chrome Extension: add jQuery to website

Question

I'm trying to add the "resizable"-functionality of jQuery UI to an existing webpage by using a Chrome extension. When using the following code, in Chrome console the error "Uncaught ReferenceError: jQuery is not defined" appears.

manifest.json:

{
    "manifest_version": 2,
    "name": "Resizeable",
    "permissions": [
          "tabs"
        ],
    "content_scripts": [{
        "all_frames": true,
        "matches": ["https://abcde.net/Tools/*"],
        "js": ["jquery-1.9.1.js","jquery-ui.js","contentscript.js"],
        "run_at": "document_end" 
        }]
}

contentscript.js:

var jq = document.createElement('script');
jq.type = 'text/javascript';
jq.src = 'https://code.jquery.com/jquery-1.9.1.js';
document.head.appendChild(jq);

var jqUI = document.createElement('script');
jqUI.type = 'text/javascript';
jqUI.src = 'https://code.jquery.com/ui/1.10.4/jquery-ui.js';
document.head.appendChild(jqUI);

if (window.jQuery && jQuery.ui) {
    alert('loaded');
} else {
    alert('not loaded');
}

I can bypass the error message by pasting each of the three "paragraphs" individually into Chrome console. Therefore, I assume that the error appears because the jQuery is not loaded completely yet when jQuery UI is added. Next, I tried the following:

contentscript.js:

var jq = document.createElement('script');
jq.type = 'text/javascript';
jq.src = 'https://code.jquery.com/jquery-1.9.1.js';
document.head.appendChild(jq);

checkJquery();

function checkJquery() {
    if(window.jQuery) {
        var jq = document.createElement('script');
        jq.type = 'text/javascript';
        jq.src = 'https://code.jquery.com/ui/1.10.4/jquery-ui.js';
        document.head.appendChild(jq);
        alert('jQ is loaded');
        checkJqueryUI();
    } else {
        setTimeout(function() {
            checkJquery();
        }, 1000);
    }
}

function checkJqueryUI() {
    if(jQuery.ui) {
        alert('UI is loaded');
        furtherCode();
    } else {
        setTimeout(function() {
            checkJqueryUI();
        }, 1000);
    }
}

function furtherCode() {
    var s = document.createElement('link');
    s.rel = 'stylesheet';
    s.href= 'https://code.jquery.com/ui/1.10.4/themes/smoothness/jquery-ui.css'
    document.head.appendChild(s); 

    var s = document.createElement('style');
    var css = '#resizable { width: 470px; height: 320px; padding: 0.5em; } #resizable h3 { text-align: center; margin: 0; }'
    s.appendChild(document.createTextNode(css));
    document.head.appendChild(s); 

    document.getElementById('bigDocFrame').parentNode.setAttribute("id", "resizable");
    document.getElementById('bigDocFrame').parentNode.setAttribute("class", "ui-widget-content");
    document.getElementById('bigDocFrame').height='100%'; 

    var s = document.createElement('script');
    s.type = 'text/javascript';
    s.language = 'javascript';
    var script = 'jQuery.noConflict();'
    s.appendChild(document.createTextNode(script));
    document.head.appendChild(s); 

    var s = document.createElement('script');
    var script = 'jQuery(function() {jQuery( "#resizable" ).resizable();});'
    s.appendChild(document.createTextNode(script));
    document.head.appendChild(s); 
}

But the condition "if(window.jQuery)" is always false. I expected it to be true after some time. Am I making a mistake? (Solved by adding jquery-1.9.1.js and jquery-ui.js to manifest.json)

Still, the error message " Uncaught ReferenceError: jQuery is not defined" appears. It is reffered to "VM5466:1", which consists of one line of code:

jQuery.noConflict();