Upload part 0

part0/0.4.md

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+# Exercise 0.4
+
+```mermaid
+sequenceDiagram
+    participant browser
+    participant server
+
+    Note right of browser: User enters new note entry and click "Save"
+
+    browser->>server: HTTP POST https://studies.cs.helsinki.fi/exampleapp/new_note
+    activate server
+
+    Note left of server: New note entry is added
+
+    server-->>browser: Redirect to https://studies.cs.helsinki.fi/exampleapp/notes
+    deactivate server
+
+    browser->>server: HTTP GET https://studies.cs.helsinki.fi/exampleapp/main.css
+    activate server
+    server-->>browser: main.css
+    deactivate server
+
+    browser->>server: HTTP GET https://studies.cs.helsinki.fi/exampleapp/main.js
+    activate server
+    server-->>browser: main.js
+    deactivate server
+
+    Note right of browser: The browser starts executing the JavaScript code that fetches the JSON from the server
+
+    browser->>server: HTTP GET https://studies.cs.helsinki.fi/exampleapp/data.json
+    activate server
+    server-->>browser: [{ "content": "HTML is easy", "date": "2023-1-1" }, ... ]
+    deactivate server
+
+    Note right of browser: The browser executes the callback function that renders the notes
+
+```

part0/0.5.md

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+# Exercise 0.5
+
+```mermaid
+sequenceDiagram
+    participant browser
+    participant server
+
+    browser->>server: HTTP GET https://studies.cs.helsinki.fi/exampleapp/spa
+    activate server
+    server-->>browser: HTML-code
+    deactivate server
+
+    browser->>server: HTTP GET https://studies.cs.helsinki.fi/exampleapp/main.css
+    activate server
+    server-->>browser: main.css
+    deactivate server
+
+    browser->>server: HTTP GET https://studies.cs.helsinki.fi/exampleapp/spa.js
+    activate server
+    server-->>browser: spa.js
+    deactivate server
+
+    Note right of browser: The browser starts executing the JavaScript code that fetches the JSON from the server
+
+    browser->>server: HTTP GET https://studies.cs.helsinki.fi/exampleapp/data.json
+    activate server
+    server-->>browser: [{"content":"","date":"2023-03-13T01:16:01.627Z"}, ... ]
+    deactivate server
+
+    Note right of browser: The browser executes the callback function that renders the notes
+
+```

part0/0.6.md

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+# Exercise 0.6
+
+```mermaid
+sequenceDiagram
+    participant browser
+    participant server
+
+    Note right of browser: User enters new note entry and click "Save"
+
+    browser->>server: HTTP POST https://studies.cs.helsinki.fi/exampleapp/new_note_spa
+    activate server
+    server-->>browser: {"message":"note created"}
+    deactivate server
+
+    Note right of browser: The browser updates the page with the new note
+
+```