JavaScript crash course for C/C++ people

This work is licensed under CC BY-SA 4.0.

Under construction. Feedbacks are welcomed.

General

1. The syntax is mostly the same as C/C++. You’re going to feel like home.

2. let works like auto in C++. const works like const auto in C++.

3. Never use == in JavaScript. Always use === and it works like == in C/C++.

4. A Number is essentially an IEEE754 double. To hold a >56 bits integer, use BigInt.

5. Variables passed to functions are passed by value.

Objects

1. Objects can be used like structs and classes. But they’re essentially a std::unordered_map<std::variant<T1, T2>, U> where T1 is String, T2 is Symbol and U could be anything.

2. Passing Objects to functions works like passing by reference in C++ or passing a pointer in C. That means you can modify the content of the Object passed to the function. But such a “reference” is indistinguishable from a value. If you use Linux and/or other Unix, the best analogy to describe those “references” is hard links on a filesystem.

3. Assigning an existing Object to a new value will still create a “reference”. They call it “Shallow Copy”. To mimic the behavior in C/C++, you need to do Deep Copy.