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| -rw-r--r-- | doc/manual.tex | 1 | ||||
| -rw-r--r-- | lib/js/urweb.js | 10 |
2 files changed, 11 insertions, 0 deletions
diff --git a/doc/manual.tex b/doc/manual.tex index ba53f5d8..62b322ae 100644 --- a/doc/manual.tex +++ b/doc/manual.tex @@ -2573,6 +2573,7 @@ It is possible to write JavaScript FFI code that interacts with the functional-r \item \cd{sr(v)} and \cd{sb(s, f)}, the ``return'' and ``bind'' monad operators, respectively \item \cd{ss(s)}, to produce the signal corresponding to source \cd{s} \item \cd{scur(s)}, to get the current value of signal \cd{s} + \item \cd{listen(s, f)}, to ask that function \cd{f} be called with the current value of \cd{s}, every time it changes, including immediately upon establishing this listener \end{itemize} \item The behavior of the \cd{<dyn>} pseudo-tag may be mimicked by following the right convention in a piece of HTML source code with a type like $\mt{xbody}$. Such a piece of source code may be encoded with a JavaScript string. To insert a dynamic section, include a \cd{<script>} tag whose content is just a call \cd{dyn(pnode, s)}. The argument \cd{pnode} specifies what the relevant enclosing parent tag is. Use value \cd{"tr"} when the immediate parent is \cd{<tr>}, use \cd{"table"} when the immediate parent is \cd{<table>}, and use \cd{"span"} otherwise. The argument \cd{s} is a string-valued signal giving the HTML code to be inserted at this point. As with the usual \cd{<dyn>} tag, that HTML subtree is automatically updated as the value of \cd{s} changes. diff --git a/lib/js/urweb.js b/lib/js/urweb.js index 66d427c8..332de6dc 100644 --- a/lib/js/urweb.js +++ b/lib/js/urweb.js @@ -2135,6 +2135,16 @@ function active(s) { } } +function listen(s, onchange) { + var x = document.createElement("script"); + x.dead = false; + x.signal = s; + x.sources = null; + x.closures = null; + x.recreate = onchange; + populate(x); +} + function input(x, s, recreate, type, name) { if (name) x.name = name; if (type) x.type = type; |