dom: fix replace child

src/dom/node.zig

@@ -294,27 +294,33 @@ pub const Node = struct {
     // function must accept either node or string.
     // blocked by https://github.com/lightpanda-io/jsruntime-lib/issues/114
     pub fn replaceChildren(self: *parser.Node, nodes: ?Variadic(*parser.Node)) !void {
+        // remove existing children
+        try removeChildren(self);
+
         if (nodes == null) return;
         if (nodes.?.slice.len == 0) return;
 
-        // remove existing children
+        // add new children
-        if (try parser.nodeHasChildNodes(self)) {
+        for (nodes.?.slice) |node| {
+            _ = try parser.nodeAppendChild(self, node);
+        }
+    }
+
+    pub fn removeChildren(self: *parser.Node) !void {
+        if (!try parser.nodeHasChildNodes(self)) return;
+
         const children = try parser.nodeGetChildNodes(self);
         const ln = try parser.nodeListLength(children);
         var i: u32 = 0;
         while (i < ln) {
             defer i += 1;
-                const child = try parser.nodeListItem(children, i) orelse continue;
+            // we always retrieve the 0 index child on purpose: libdom nodelist
+            // are dynamic. So the next child to remove is always as pos 0.
+            const child = try parser.nodeListItem(children, 0) orelse continue;
             _ = try parser.nodeRemoveChild(self, child);
         }
     }
 
-        // add new children
-        for (nodes.?.slice) |node| {
-            _ = try parser.nodeAppendChild(self, node);
-        }
-    }
-
     pub fn deinit(_: *parser.Node, _: std.mem.Allocator) void {}
 };