【重构map】【重构filter】【重构Some】【重构reduce方法】【重构flat函数】

重构map

var arr = [1,3,4,5,5];
Array.prototype.myMap = function(callback,item){
    
    var arr = [];
    for(var i=0;i<this.length;i++){
    
        var temp = callback(this[i],i,this);
        arr.push(temp);
    }
    return arr;

}
arr = arr.myMap(function(item,index){
    
    return item*2
})
console.log(arr);//[2, 6, 8, 10, 10]
</script>

重构filter

Array.prototype.myFilter = function(callback){
    
    var arr = [];
    for(var i=0;i<this.length;i++){
    
        if(callback(this[i],i,this)){
    
            arr.push(this[i]);
        }
    }
    return arr
}
arr = arr.myFilter(function(item){
    
    return item > 3
})

console.log(arr);//[4, 5, 5]

重构Some

Array.prototype.mySome = function(callback){
    
    var arr = [];
    for(var i=0;i<this.length;i++){
    
        if(callback(this[i])){
    
            return true;
        }
    }
    return false
}
arr = arr.mySome(function(item){
    
    return item > 7
})

重构reduce方法

arr = [1, 2, 3]
Array.prototype.myReduce = function (callback, init) {
    
    var start = init === undefined ?1:0;
    init = init ?? this[0];
    for (var i = start; i < this.length; i++) {
    
        var init = callback(init, this[i])
    }
    return init;
}
var sulter = arr.myReduce(function (v, t) {
    
    return v + t;
},2)
console.log(sulter);

重构flat函数

Array.prototype.myFlat = function(depth = 1){
    
    if(depth == 0) return this;
    console.log('this=',this);
    return  this.reduce((v,t)=>{
    
        if(Array.isArray(t)){
    
            return [...v,...t.myFlat(depth-1)]
        }else{
    
            return [...v,t]
        }
    },[])
    
}
arr= [1,2,3,3,[36,9,9,[0]]]
arr = arr.myFlat()
console.log(arr);//[1, 2, 3, 3, 36, 9, 9, Array(1)]