Truthy and default values
What does the code print? Compare boolean conversion with || and ??. Enter one line with | separators.
Solve challenge → No login requiredJAVASCRIPT IN PRACTICE
Understand JavaScript
Predict output, understand type conversions and work out the order of asynchronous operations.
- Type conversion
- Data flow
- Execution order
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Async Order
Analyze the Event Loop. What exactly will the console output?
Solve challenge → No login requiredYYYY-MM-DD format
Match a date in YYYY-MM-DD format. Check the shape only: 4 ASCII digits, hyphen, 2 digits, hyphen, 2 digits. Do not validate the calendar; 2024-99-99 matches.
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How should you approach these challenges?
JavaScript code analysis helps you understand an unexpected result before changing the implementation. You practise reasoning used in code reviews, debugging and explaining application behaviour to teammates.
Read the code one operation at a time and note intermediate values and their types. Separate immediate execution from scheduled work. For regex, encoded data and security tasks, first identify the rule you are checking, then look for an example that could disprove it.
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