js-on-sx: baseline commit (278/280 unit, 148/148 slice, runner stub)

Initial commit of the lib/js/ tree and plans/ directory. A previous
session left template-string work in progress — 278/280 unit tests pass
(2 failing: tpl part-count off-by-one, escaped-backtick ident lookup).
test262-runner.py and scoreboard are placeholders (0/8 with 7 timeouts);
fixing the runner is the next queue item.

lib/js/test262-slice/errors/error_message.expected

@@ -0,0 +1 @@
+oops

lib/js/test262-slice/errors/error_message.js

@@ -0,0 +1,3 @@
+var m;
+try { throw new Error("oops"); } catch(e) { m = e.message; }
+m

lib/js/test262-slice/errors/throw_catch_string.expected

@@ -0,0 +1 @@
+boom

lib/js/test262-slice/errors/throw_catch_string.js

@@ -0,0 +1,3 @@
+var msg;
+try { throw "boom"; } catch(e) { msg = e; }
+msg

lib/js/test262-slice/errors/throw_in_function.expected

@@ -0,0 +1 @@
+div by zero

lib/js/test262-slice/errors/throw_in_function.js

@@ -0,0 +1,7 @@
+function divide(a, b) {
+  if (b === 0) throw new Error("div by zero");
+  return a / b;
+}
+var result;
+try { result = divide(10, 0); } catch(e) { result = e.message; }
+result

lib/js/test262-slice/errors/try_finally.expected

@@ -0,0 +1 @@
+3

lib/js/test262-slice/errors/try_finally.js

@@ -0,0 +1,3 @@
+var x = 0;
+try { x = 1; throw "e"; } catch(e) { x = 2; } finally { x = 3; }
+x

lib/js/test262-slice/errors/typeerror_name.expected

@@ -0,0 +1 @@
+TypeError

lib/js/test262-slice/errors/typeerror_name.js

@@ -0,0 +1,3 @@
+var n;
+try { throw new TypeError("bad type"); } catch(e) { n = e.name; }
+n