去重 es5 VS es6

Posted 2020-11-05 rubyhelloworld

 一、数组去重的方式
//1循环一次 
 var arr1 = [1,2,3,44,44,11,2,3,333,3,3];
    function removeRepeat(arr){
        var removeArr = [],obj = {};
        for(var i = 0, l = arr.length; i < l; i++){
            if(!obj[arr[i]]){
                removeArr.push(arr[i]);
                obj[arr[i]] = 1;
            }
        };
        return removeArr;
    }
    var singleArr = removeRepeat(arr1);
    console.log(singleArr); //[1, 2, 3, 44, 11, 333]

function unique(arr){
  var obj = {}
  var result = []
  for(var i in arr){
    if(!obj[arr[i]]){
      obj[arr[i]] = true;
      result.push(arr[i]);
    }
  }
  return result;
}

 function remove2(arr){
        return Array.from(new Set(arr));
    }
    var single2 = remove2(arr1);
    console.log(single2)  //[1, 2, 3, 44, 11, 333] es6 语法  其实问数组的去重主要是考上面一种思维方式
二、返回字符串中字符出现次数最多的那字符

var str = "abbcccddddfffffgggggg";

    function maxNum(str){

        if(str.length <= 1){
            return str;
        }

        var a1 = str.split(‘‘),obj = {},result = [];
        //利用上面一个数组去重的思想
        for(var k = 0, l = a1.length; k < l; k++){
            if(!obj[a1[k]]){
                obj[a1[k]] = 1;
            }else {
                obj[a1[k]] += 1;
            };
        }

        var num = 0, word = "";
        for(var item in obj){
            if(obj[item] > num){
                num = obj[item];
                word = item;
            }
        }
        return word;
    }
    var w = maxNum(str);
    console.log(w);   //g