How should the return value of JavaScript links be handled?

问题

According to standards, what's the correct way to handle the return value of javascript protocol href links?

Some examples:

<a href='javascript:"Hello World";'> Click </a> <!-- return a String -->

<a href='javascript:ThisFunctionReturnsString();'> Click </a>

<a href='javascript:12345;'> Click </a> <!-- Number -->

<a href='javascript:[1, 2, 3, 4, 5];'> Click </a> <!-- Array -->

<a href='null;'> Click </a> <!-- null-->

<a href='undefined;'> Click </a> <!-- undefined-->

<a href='javascript:{};'> Click </a> <!-- Object -->

How should a standard-compliant browser handle the return values?

How do current browsers in the wild differ from this standard behavior?

回答1:

From Web Applications API §6.1.5:

The following explains why clicking the links replaces the document content:

If the result of executing the script is void (there is no return value), then the URL must be treated in a manner equivalent to an HTTP resource with an HTTP 204 No Content response.

Otherwise, the URL must be treated in a manner equivalent to an HTTP resource with a 200 OK response whose Content-Type metadata is text/html and whose response body is the return value converted to a string value.

This behavior can also be demonstrated easily by simply pasting javascript:"Hello World"; in the address bar. Same goes for javascript:(function() { return "Hello World";})().

And the following explains why only your 1 and 2 code snippets are actually doing something.