问题 I apologize for posting a duplicate-looking question, (I know, that there is a bunch of similar titled questions here), but none of the questions already present seems to suit my case. In short, what does the colon do here: <script> 'use strict'; foo: 1; //whatever else </script> I supposed this to be a syntax error, but it's not. And it's not a label, I think, since adding a line break foo; throws Uncaught SyntaxError: Undefined label 'foo' (though a doc page suggests exactly this, that it's