Set

集合

by Chris_Walter

JavaScript

class Set{
  constructor(){
	  this.items = {};
	}
	has(value){
	  return this.items.hasOwnProperty(value);
	}
	add(value){
	  //如果這個值不存在才新增至物件，存在則直接回傳false
	  if(!this.has(value)){
		  this.items[value] = value;
			return true;
		}
		return false;
	}
	remove(value){
	  if(this.has(value)){
		  delete this.items[value];
			return true;
		}
		return false;
	}
	clear(){
	  this.items = {};
	}
	size(){
	  return Object.keys(this.items).length;//只能在現代瀏覽器中運行
	}
	/*
	sizeLegacy(){
	  let count = 0;
	  for(let num in this.items){
		  if(this.has(num)){
			  ++count;
			}
		  return count;
		}
	}
	*/
	values(){
	  return Object.keys(this.items);
	}
	/*
	valuesLegacy(){
	  let keys = [];
		for(let key in this.items){
		  keys.push(key);
		}
		return keys;
	}
	*/
	//聯集
	union(otherSet){
	  let unionSet = new Set();
		let values = this.values();
		for(let i=0; i<values.length; i++){
		  unionSet.add(values[i]);
		}
		values = otherSet.values();
		for(let i=0; i<values.length; i++){
		  unionSet.add(values[i]);
		}
		return unionSet
	}
	//交集
	intersection(otherSet){
	  let intersectionSet = new Set();
		let values = this.values();
		for(let i=0; i<values.length; i++){
		  if(otherSet.has(values[i])){
			  intersectionSet.add(values[i]);
			}
		}
		return intersectionSet;
	}
	//差集
	difference(otherSet){
	  let differenceSet = new Set();
		let values = this.values();
		for(let i=0; i<values.length; i++){
		  if(!otherSet.has(values[i])){
			  differenceSet.add(values[i]);
			}
		}
		return differenceSet;
	}
	//子集
	subSet(otherSet){
	  let values = this.values();
		if(this.size() > otherSet.size()){
		  return false;
		} else {
		  for(let i=0; i<values.length; i++){
		    if(!otherSet.has(values[i])){
			    return false;
			  }
		  }
			return true;
		}
	}
}

let n1 = new Set();
n1.add('Alan');
console.log(n1);
n1.remove('Alan');
console.log(n1);
console.log(n1.size());
n1.add('John');
console.log(`size: ${n1.size()}`);
//console.log(`sizeLegacy: ${n1.sizeLegacy()}`);

let nA...