Evaluator

An evaluator of a stripped down version of JS, aiming to replicate REPL of Node.js.

Installation

You can run this project in 2 ways:

1. Install the .jar from the releases section, and then run java -jar jseval-v1.0.jar [-gui | -help]
2. Clone the repo and open the project in IntelliJ. Then simply run the Main.kt file located in src/main/kotlin/Main.kt.

Example Usage

Supports:

• Statements:
  • Variable Declarations
  • Function Declarations
    • Pure functions defined like:

    • function double(x) {
        return x * 2;
      }
      

  • Loops/Conditional Statements are yet to be implemented.
• Expressions
  • Arithmetic operations of +, -, *, /
  • Comparison operations of >, <, ==, >=, <=
  • Logical operations of &&, ||, !
  • Assignment
  • Function call expressions
  • Variable References
  • Literals (values)

Tests:

Tests are contained in src/test/ directory. The tests are:

• EvalTests.kt
  • Tests core evaluation functionality
• ParseTests.kt
  • Tests core parsing functionality

Commands

You can use the following commands in the interactive session:

• info: displays information about all the variables, their modifier types, and their values.
• assign [varname] [varvalue]:
  • assigns a variable to a value (NOTE: the variable should be declared first)
  • varvalue can also be an expression (e.g. assign a c+4)
• evalLine [lineno]: evaluates the given line number and returns the result if it is an expression
• invoke [funcname] [args separated by comma]: invokes a function with the given arguments and returns the result

TODO

• conditional / loop statement support
• Implement support for ES named imports:

    import { foo, bar } from "/modules/my-module.js";
    let x = 1 + foo;
    let y = 2 * bar;
    x + y