You can use a Javascript bookmark: https://helloacm.com/how-to-write-chrome-bookmark-scripts-step-by-step-tutorial-with-a-steemit-example/. Just create a bookmark to look like this:
Ex:
Name:
Test javascript bookmark in Chrome
URL:
javascript:alert('Hello world!');
Just precede the URL with javascript:
, followed by your Javascript code. No space after the colon is required.
Here's how it looks as I'm typing it in:
Now save and then click on your newly-created Javascript bookmark, and you'll see this:
You can do multi-line scripts too. If you include any comments, however, be sure to use the C-style multi-line comments ONLY (/* comment */
), and NOT the C++-style single-line comments (// comment
), as they will interfere. Here's an example:
URL:
javascript:
/* This is my javascript demo */
function multiply(a, b)
{
return a * b;
}
var a = 1.4108;
var b = 3.7654;
var result = multiply(a, b);
alert('The result of ' + a + ' x ' + b + ' = ' + result.toFixed(4));
And here's what it looks like as you edit the bookmark, after copying and pasting the above multi-line script into the URL field for the bookmark:
And here's the output when you click on it: