SOURCE

// 原理就是不断向上找数值的prototype去匹配给定的类型 

function myInstanceof (left, right){
    let proto = Object.getPrototypeOf(left)
    while(true){
        if(proto == right.prototype) return true
        if(proto != null) return false
        proto = Object.getPrototypeOf(proto)
    }
}

let a = []
console.log(myInstanceof(a, Object))