總結了一下js中的差集、交集、並集

前言

總結了一下有關於數組的差集、交集、並集的方法；

es6的方法實現

去重

/**
 * 簡單的數組去重
 * @param {Array} a 
 */
const uniquelize = function(a) {
  if (a.constructor !== Array) {
    throw TypeError("請傳入數組類型");
  }
  return Array.from(new Set(a));
};

並集

/**
 * 簡單數組的並集
 * @param {Array} a 
 * @param {Array} b 
 */
const getUnion = function(a,b){
    if(a.constructor === Array && b.constructor === Array){
        let set1 = new Set(a);
        let set2 = new Set(b);
        return Array.from(new Set([...set1,...set2]));
    }
    return null;
}

交集

/**
 * 簡單數組的交集
 * @param {Array} a 
 * @param {Array} b 
 */
const getIntersect = function(a,b){
    if(a.constructor === Array && b.constructor === Array){
        let set1 = new Set(a);
        let set2 = new Set(b);
        return Array.from(new Set([...set1].filter( x => set2.has(x))));
    }
    return null;
}

差集

/**
 * 簡單數組的差集
 * @param {Array} a 
 * @param {Array} b 
 */
const getDifference = function(a,b){
    if(a.constructor === Array && b.constructor === Array){
        let set1 = new Set(a);
        let set2 = new Set(b);
        return Array.from(new Set([...set1].filter(x => !set2.has(x))));
    }
    return null;
}

es5的方法實現

去重

/**
 * 簡單的數組去重
 * @param {Array} a 
 */
var uniquelize = function(a) {
  if (a.constructor !== Array) {
    throw TypeError("請傳入數組類型");
  }
  var obj = {},
    arr = [];
  for (var i = 0, j = a.length; i < j; i++) {
    if (!obj[a[i]]) {
      obj[a[i]] = 1;
      arr.push(a[i]);
    }
  }
  return arr;
};

交集

/**
 * 簡單數組的交集
 */
var getIntersect = function(){
    var arr = new Array();
    var obj = new Object();
    var arguLen = arguments.length;
    for(var i = 0; i<arguLen;i++){
        if(arguments[i].constructor !== Array){
            throw TypeError("請都傳入數組類型");
        }
        for(var j = 0,length = arguments[i].length;j<length;j++){
            var item = arguments[i][j];
            if(!obj[item]){
                obj[item] = 1;
            }else{
                obj[item]++;
                if(obj[item]===arguLen){
                    arr.push(item);
                }
            }
        }
    }
    return arr;
}

並集

/**
 * 簡單數組的並集
 */
var getUnion = function(){
    var arr = new Array();
    var obj = new Object();
    var arguLen = arguments.length;
    for(var i = 0; i<arguLen;i++){
        if(arguments[i].constructor !== Array){
            throw TypeError("請都傳入數組類型");
        }
        for(var j = 0,length = arguments[i].length;j<length;j++){
            var item = arguments[i][j];
            if(!obj[item]){
                obj[item] = 1;
                arr.push(item);
            }else{
                //統計一下出現了多少次
                obj[item]++;
            }
        }
    }
    return arr;
}

差集

/**
 * 簡單數組的差集
 */
var getDifference = function(){
    var arr = new Array();
    var obj = new Object();
    var arguLen = arguments.length;
    for(var i = 0; i<arguLen;i++){
        if(arguments[i].constructor !== Array){
            throw TypeError("請都傳入數組類型");
        }
        for(var j = 0,length = arguments[i].length;j<length;j++){
            var item = arguments[i][j];
            if(!obj[item]){
                obj[item] = 1;
                arr.push(item);
            }else{
                obj[item]++;
                var index = arr.indexOf(item);
                //存在就刪除掉
                if(index !== -1){
                    arr.splice(index,1);
                }
            }
        }
    }
    return arr;
}