Can the label "javascript:" cause any problems?

Question

Both JSLint and JSHint issue warnings when they encounter a labelled statement whose identifier matches the following regular expression:

/^(?:javascript|jscript|ecmascript|vbscript|mocha|livescript)\s*:/i

For example, the following snippet generates a "JavaScript URL" warning from JSLint and a "Label 'javascript' looks like a javascript url" warning from JSHint (the function wrapper is unnecessary, but JSLint doesn't like labelled statements that are not function-scoped and raises a different warning):

function example(x, y) {
javascript:
    while (x) {
        while (y) {
            break javascript;
        }
    }
}

As far as I can tell, no browser cares about it, even when it appears immediately after the "javascript:" protocol in a bookmarklet. For example, the following always seem to work (just paste into the address bar like any bookmarklet):

javascript:(function () { javascript:for(var i = 0; i < 2; i++) { alert(i); break javascript; } }());

javascript:javascript:for(var i = 0; i < 2; i++) { alert(i); break javascript; }

Could the label identifier "javascript:" (or any other string that would match that regex) ever have caused any issues (some ancient browser perhaps?) that would warrant the warnings generated? Why are these warnings generated?

Answer 1

I'm mostly guessing here, but consider that:

• javascript: is not an actual protocol;
• it's not needed anywhere except bookmarklets (otherwise it's assumed to be a label);
• the warning says it "looks like a javascript url".

I think JSLint is suggesting that the javascript: pseudo-protocol is bad, and so is anything that resembles it, or could be confused with it. Could it cause any problems? Strictly speaking, perhaps on IE (maybe oldIE only). But, as I said, a javascript: label might be confused with the pseudo-protocol, and JSLint doesn't like anything potentially confusing. So, this might be an explanation.