Blockly-Junior is version of Blockly for young children that have not learned to read yet (3-5 year-olds). It is similar to [ScratchJr] (https://www.scratchjr.org/), which is a simpler version of [Scratch] (https://scratch.mit.edu/).
See the web site with a live demo.
Google's Blockly is a web-based, visual programming editor. Users can drag blocks together to build programs. All code is free and open source.
The project page is https://developers.google.com/blockly/