JS-BASIC

A javascript based minimal basic toy compiler and runtime envionment

Objectives

• Create a frontend only minimal UI
• Striped Editor where code will be written
• Emulated Terminal, that can print
• Emulated Terminal, that can handle input with callbacks
• Run/Clear Button
• Create a lexer, that can parse raw code and generated tokenised code
• Create a parser, that can parse tokenised code and generated op code
• Create a runtime, that can run op code and interact with emulated terminal for output and input
• Debugging Controls
• Show variable and call stack while debugging mode
• Show syntax errors

Supported Commands

The runtime should be able to handle the below basic commands

Data manipulation:

• LET—assigns a value (which may be the result of an expression) to a variable.
• DATA—holds a list of values which are assigned sequentially using the READ command.
• READ-reads data from DATA statements into variables

Program flow control:

• IF ... THEN ... {ELSE}—used to perform comparisons or make decisions.
• FOR ... TO ... {STEP} ... NEXT—repeat a section of code a given number of times. A variable that acts as a counter is available within the loop.
• WHILE ... WEND—repeat a section of code while the specified condition is true. The condition may be evaluated before each iteration of the loop.
• REPEAT ... UNTIL—repeat a section of code while the specified condition is true. The condition may be evaluated after each iteration of the loop.
• DO ... LOOP {WHILE} or {UNTIL}—repeat a section of code Forever or While/Until the specified condition is true. The condition may be evaluated before each iteration of the loop, or after.
• GOTO—jumps to a numbered or labelled line in the program.
• GOSUB—jumps to a numbered or labelled line, executes the code it finds there until it reaches a RETURN Command, on which it jumps back to the operator following the GOSUB – either after a colon, or on the next line. This is used to implement subroutines.
• ON ... GOTO/GOSUB—chooses where to jump based on the specified conditions. See Switch statement for other forms.

Input and output:

• PRINT—displays a message on the screen or other output device.
• INPUT—asks the user to enter the value of a variable. The statement may include a prompt message.

List of functions:

• ABS—Absolute value
• ATN—Arctangent value (result in radians)
• COS—Cosine value (argument in radians)
• EXP—Exponential value
• INT—Integer value
• LOG—Natural Logarithmic value
• RND—Random value
• SIN—Sine value (argument in radians)
• SQR—Square root value
• TAN—Tangent value (argument in radians)