for (var index = 0; index < myArray.length; index++) {
 console.log(myArray[index]);
}

myArray.forEach(function (value) {
 console.log(value);
});

for (var index in myArray) { 
 console.log(myArray[index]);
}

for (var value of myArray) {
 console.log(value);
}

var a = ["a","b","c","d","e"];
for (var idx in a) {
  console.log( idx ); 
  }// 0 1 2 3 4 
for (var val of a) {
  console.log( val ); 
  }// "a" "b" "c" "d" "e"

var m = new Map([['Michael', 95], ['Bob', 75], ['Tracy', 85]]);
m.get('Michael'); // 95
var m = new Map(); // 空Map
m.set('Adam', 67); // 添加新的key-value
m.set('Bob', 59);
m.has('Adam'); // 是否存在key 'Adam': true
m.get('Adam'); // 67
m.delete('Adam'); // 删除key 'Adam'
m.get('Adam'); // undefined

var s1 = new Set(); // 空Set
var s2 = new Set([1, 2, 3]); // 含1, 2, 3
var s = new Set([1, 2, 3, 3, '3']);
s; // Set {1, 2, 3, "3"}

var uniqueWords = new Set(words);
for (var word of uniqueWords) {
 console.log(word);
}

for (var [key, value] of phoneBookMap) {
 console.log(key + "'s phone number is: " + value);
}

for (var key of Object.keys(someObject)) {
 console.log(key + ": " + someObject[key]);
}