Minimal instruction set

asm.js

const add = (memory, dest, src) => {
  memory[dest] += memory[src]
}

const addV = (memory, dest, value) => {
  memory[dest] += value
}

const sub = (memory, dest, src) => {
  memory[dest] -= memory[src]
}

const subV = (memory, dest, value) => {
  memory[dest] -= value
}

const copy = (memory, dest, src) => {
  memory[dest] = memory[src]
}

const set = (memory, dest, value) => {
  memory[dest] = value
}

const jmp = (memory, src) => {
  return memory[src]
}

const jmpV = (_memory, value) => {
  return value
}

const jmpz = (memory, dest, src) => {
  if (memory[src] === 0)
    return memory[dest]
}

const jmpVZ = (memory, value, src) => {
  if (memory[src] === 0)
    return value
}

const instr = { add, addV, sub, subV, copy, set, jmp, jmpV, jmpz, jmpVZ }

const memory = new Uint8Array(256)

const program = [
  // 0 - i = 0
  'set 0 0',
  // 1 - length = 10
  'set 1 10',
  // 2 - result = 0
  'set 2 0',
  // :loop
  // 3 - result += i
  'add 2 0',
  // 4 - i += 1
  'addV 0 1',
  // 5 - length -= 1
  'subV 1 1',
  // 6 - if length == 0
  'jmpVZ 8 1',
  // 7 - else
  'jmpV 3',
  // 8 - break
  'brk'
]

const parse = (instruction) => {
  const [op, ...argSegs] = instruction.split(' ')
  const args = argSegs.map(Number)

  return [op, ...args]
}

const execute = (program) => {
  const parsed = program.map(parse)
  let counter = 0
  let [op, ...args] = parsed[counter]

  while (op !== 'brk') {
    const result = instr[op](memory, ...args)

    if( typeof result === 'number' )
      counter = result
    else 
      counter++

    [op, ...args] = parsed[counter]
  }
}

const logMemory = () => console.log(
  ...Array.from(memory).map(v => String(v).padStart(3, ' ')), 
  '\n'
)

logMemory()
execute(program)
logMemory()