let virtualMachine = function (program) { let programCounter = 0 let stack = [] let stackPointer = 0 while (programCounter < program.length) { let currentInstruction = program[programCounter] switch (currentInstruction) { case 'PUSH': stack[stackPointer] = program[programCounter + 1] stackPointer++ programCounter++ break case 'ADD': right = stack[stackPointer - 1] stackPointer-- left = stack[stackPointer - 1] stackPointer-- stack[stackPointer] = left + right stackPointer++ break case 'MINUS': right = stack[stackPointer - 1] stackPointer-- left = stack[stackPointer - 1] stackPointer-- stack[stackPointer] = left - right stackPointer++ break } programCounter++ } console.log('stacktop: ', stack[stackPointer - 1]) } // (3 + 4) - 5 let program = ['PUSH', 3, 'PUSH', 4, 'ADD', 'PUSH', 5, 'MINUS'] virtualMachine(program)