Adding JavaScript contained in a variable as a script element

Question

The powers that be have asked me to look into this and as much as I think it's not possible I want to be sure before going back to them. Don't ask me why they want this haha

They want to be able to use JavaScript that is defined in a variable. Let me explain...

Let's say you have this variable:

var testvar = "function dan() { alert('hello world'); }";

They want to be able to call dan() and have an alert popup in the web page. Something like this doesn't appear to be useable (of course).

var importjs = document.createElement('script');
importjs.src = testvar;
document.getElementsByTagName("head")[0].appendChild(importjs);

Any ideas or jargon I can use to explain why it's not doable. I believe it's essentially a cross origin issue. Our solution requires users to install software, which uses web sockets. This software performs a file GET for the JS and we then want to use the JS in the browser.

https://stackoverflow.com/questions/939326/execute-javascript-code-stored-as-a-string — epascarello, Aug 23 '18 at 15:27

score 2 · Accepted Answer · answered Aug 23 '18 at 15:33

2

You should set the innerHTML of the script element to your String. The src of a script element should only be used to load an external script.

var testvar = "function dan() { alert('hello world'); }";
var importjs = document.createElement('script');
importjs.innerHTML = testvar;
document.getElementsByTagName("head")[0].appendChild(importjs);
dan();

answered Aug 23 '18 at 15:33

Unmitigated

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This seems to be better than the eval() answer by. In your opinion is your answer a better practice? – Dan James Palmer Aug 23 '18 at 15:36
@DanJamesPalmer `eval` should be avoided in most cases (it is both dangerous and slow). – Unmitigated Aug 23 '18 at 15:40

Adding JavaScript contained in a variable as a script element

1 Answers1