javaScript) map 자료형 for문 사용하기

	//참고 https://javascript.info/map-set
	new Map() – creates the map.
	map.set(key, value) – stores the value by the key.
	map.get(key) – returns the value by the key, undefined if key doesn’t exist in map.
	map.has(key) – returns true if the key exists, false otherwise.
	map.delete(key) – removes the value by the key.
	map.clear() – removes everything from the map.
	map.size – returns the current element count.
	let map = new Map();
	map.set('1', 'str1'); // a string key
	map.set(1, 'num1'); // a numeric key
	map.set(true, 'bool1'); // a boolean key
	// remember the regular Object? it would convert keys to string
	// Map keeps the type, so these two are different:
	alert( map.get(1) ); // 'num1'
	alert( map.get('1') ); // 'str1'
	alert( map.size ); // 3
	////////////////////////////////////////////////////////////
	///// for문 ////////////////////////////////////////////////
	let recipeMap = new Map([
	['cucumber', 500],
	['tomatoes', 350],
	['onion', 50]
	]);
	// iterate over keys (vegetables)
	for (let vegetable of recipeMap.keys()) {
	alert(vegetable); // cucumber, tomatoes, onion
	}
	// iterate over values (amounts)
	for (let amount of recipeMap.values()) {
	alert(amount); // 500, 350, 50
	}
	// iterate over [key, value] entries
	for (let entry of recipeMap) { // the same as of recipeMap.entries()
	alert(entry); // cucumber,500 (and so on)
	}
	////////////////////////////////////////////////////////////
	//////////// forEach 문/////////////////////////////////////
	// runs the function for each (key, value) pair
	recipeMap.forEach( (value, key, map) => {
	alert(`${key}: ${value}`); // cucumber: 500 etc
	});

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