JavaScript design pattern (4)-iterator pattern

  The core of the iterator pattern is to provide a way for you to traverse every element in the object and do similar processing to them.

  It's what people say-a common array processing method. Such as forEach, map, some, every and so on, usually we use to deal with array methods to give them a tall name is iterator.

  In JavaScript, in addition to arrays, ordinary objects can also be traversed by for in, so we can write a general iterator to deal with "objects".

function iterator(obj,fn){
	if (Object.prototype.toString.call(obj) === "[object Array]") {
  	for(let i=0;i<obj.length;i++){
  		fn.call(null,obj[i],i)
  	}
  }else if(Object.prototype.toString.call(obj)==='[object Object]'){
     for(let i in obj){
     	fn.call(null,obj[i],i)
     }
  }else{
     throw new Error('请传入一个数组或对象')
  }
}
iterator([3,6,9],function(val,index){
	console.log(val,index)
})
iterator({
	'a':'aaa',
	'b':'bbb'
},function(val,key){
	console.log(val,key)
})