Create a Bookmark containing Action/Javascript from the Console

I have this javascript that I run from the Console to create a bookmark containing an Javascript Action.

var root = this.bookmarkRoot;
var bookmark1 = root.createChild("Form Highlight On/Off", function() {
    app.runtimeHighlight = !app.runtimeHighlight;
});

The bookmark is created but, with this as javascript:

function() {
    app.runtimeHighlight = !app.runtimeHighlight;
}

I can’t figure out to not create a function, like so:

app.runtimeHighlight = !app.runtimeHighlight;

or to create a named one:

function bm() {
    app.runtimeHighlight = !app.runtimeHighlight;
}
bm();

How?

Thanks!