JavaScript Engine

Question 0

Engine:

What are the 3 basic tasks a JavaScript compiler completes before the code executes?

Answer 0

Tokenization: breaking up a string of characters into meaning pieces.

Parsing: arranging the tokens into a usable order called an abstract syntax tree.

Code-Generation: creating usable code and if possible performing optimization.

Question 1

Engine:
True/False

JavaScript is not complied because it is “dynamic.”

Answer 1

False

JavaScript is complied before it executes even though it is considered an “interpreted” language.

Understanding the steps the compiler takes is important to understanding how JavaScript works.

Question 2

Engine:

How will automatic semicolon insertion (ASI) modify this statement?

return
{myObject: “some value”}

Answer 2

return;
{myObject: “some value”};

So this statement will alway return “undefined” and the object will be ignored.

This happens because a new line follows the keyword “return.” This rule also applies when a new line follows continue, break and throw.

Question 3

Engine:
True/False

The JavaScript complier is called a JIT compiler.

Answer 3

False.

The JIT or just in time compiler is an optimization technique used by many compilers to precompile code. It is not the actual compiler.