js achieve instanceof

    instanceof is judged by the prototype chain, A instanceof B, layers of chain A look at the prototype, the prototype of whether there is equal B.prototype, if you have been to find the top chain of null A prototype is still not equal to B.prototype, then return false otherwise, it returns true.

   

function instance(left,right){
      left=left.__proto__
      right=right.prototype
      while(true){
           if(left==null)
                return false;
           if(left===right)
                return true;
           left=left.__proto__
      }
}