编译原理实战入门：用 JavaScript 写一个简单的四则运算编译器（三）模拟执行

function CpuEmulator(instructions) {
    this.ins = instructions.split('\r\n')
    this.memory = []
    this.re = /^(push)\s\w+/
    this.execute()
}
CpuEmulator.prototype = {
    execute() {
        this.ins.forEach(i => {
            switch (i) {
                case 'add':
                    this.add()
                    break
                case 'sub':
                    this.sub()
                    break
                case 'mul':
                    this.mul()
                    break
                case 'div':
                    this.div()
                    break                
                default:
                    if (this.re.test(i)) {
                        this.push(i.split(' ')[1])
                    }
            }
        })
    },
    add() {
        const b = this.pop()
        const a = this.pop()
        this.memory.push(a + b)
    },
    sub() {
        const b = this.pop()
        const a = this.pop()
        this.memory.push(a - b)
    },
    mul() {
        const b = this.pop()
        const a = this.pop()
        this.memory.push(a * b)
    },
    div() {
        const b = this.pop()
        const a = this.pop()
        this.memory.push(a / b)
    },
    push(x) {
        this.memory.push(parseInt(x))
    },
    pop() {
        return this.memory.pop()
    },
    getResult() {
        return this.memory[0]
    }
}