手写数组的方法

[ichanghe]

forEach:

Array.prototype.myForEach = function(cb){
    var _arr = this;
    var _len = _arr.length;
    var _arg2 = arguments[1]||window
    for(let i=0;i<_len;i++){
        cb.apply(_arg2,[_arr[i],i,_arr])
    }
}

map和 filter:

Array.prototype.myMap = function(cb){
    var _arr = this;
    var _len = _arr.length;
    var _arg2 = arguments[1]||window
    var _newArr = [];
    var _item;
    var res;
    for(let i=0;i<_len;i++){
        _item = deepClone(arr[i])
        
       _res =  cb.apply(_arg2,[item,i,_arr])
       _res&& _newArr.push(_res)
    }
    return _newArr;
}

Array.prototype.myFilter = function(cb){
    var _arr = this;
    var _len = _arr.length;
    var _arg2 = arguments[1]||window
    var _newArr = [];
    var _item;
    var res;
    for(let i=0;i<_len;i++){
        _item = JSON.parse(JSON.stringify(arr[i])))
        
       cb.apply(_arg2,[_item,i,_arr])?_newArr.push(_item):''
    }
    return _newArr;
}

some:

Array.prototype.mySome = function (cb){
    var _arr = this
    var _length = _arr.length
    var args = arguments[1] || window
    var status = false
    for(let i=0;i<_length;i++){
      let result =  cb.apply(args,[_arr[i],i,_arr])    
      if(result) status = true
    }
    return status
}

every:

Array.prototype.myEvery = function (cb){
    var _arr = this
    var _length = _arr.length
    var args = arguments[1] || window
    for(let i=0;i<_length;i++){
      let result =  cb.apply(args,[_arr[i],i,_arr])    
      if(!result) return false
    }
    return true
}

slice:

Array.prototype.mySlice = function (start, end) {
    var result = new Array();
    start = start || 0;
    end = end || this.length; //this指向调用的对象，当用了call后，能够改变this的指向，也就是指向传进来的对象，这是关键
    for (var i = start; i < end; i++) {
        result.push(this[i]);
    }
    return result;
};

reduce:

Array.prototype.myReduce = function(cb,initialValue){
    var _arr = this
    var _length = _arr.length
    for(var i =0;i<_length;i++){
      	initialValue =  cb.apply(null,[inititalValue,])
    }
    return initialValue
}

reduceRight:

Array.prototype.myReduce = function(cb,initialValue){
    var _arr = this
    var _length = _arr.length
    for(var i =_length;i>0;i--){
      	initialValue =  cb.apply(null,[inititalValue,])
    }
    return initialValue
}