Question

I’m including some 3rd party code in my application and I see that it uses document.write() code which is wrapped in a try..catch statement.
The document.write() doesn’t return anything, so I wanted to know is there a way to test if document.write() was successful, so I can test catching the error.
As an example, I tried including this script async but this stopped the document.write() part executing but it didnt run the code in the catch() part.

example code:

try {
   document.write('<script type="text/javascript" src="/plugin.js">');
   console.log('OK');
} catch (e) {
   console.log('ERROR');
}

Answer 1

You can add id to script tag and then fetch it from DOM by id:

document.write('<script type="text/javascript" src="/plugin.js" id="myscript"></script>');
if (document.getElementById('myscript')) {
    console.info('success');
} else {
    console.error('failure');
}

or you can try to find it in all scripts on page if you don’t want to change anything:

document.write('<script type="text/javascript" src="/plugin.js"></script>');
(function () {
    var scripts = document.getElementsByTagName('script'),
        l = scripts.length - 1;
    // If you'll check that just after document.write then it should be last script
    // in the other case you would need to check all scripts.
    // From src I'm removing domain - at least Safari is returning full URL here
    if (scripts.length && scripts[l - 1].src && scripts[l - 1].src.replace(/^([a-z]+:\/\/[^\/]*)/i, '') == '/plugin.js') {
        console.info('success');
    } else {
        console.error('failure');
    }
}());