js中的Map

/*
* js中的map
*/
function myJsMap() {

var myMap = {};
myMap["key1"] = "value1";
myMap["key2"] = "value2";
myMap["key3"] = "value3";

if ("key2" in myMap) {
alert("key2 = " + myMap["key2"]);
}

delete myMap["key2"];

for (var key in myMap) {
alert(key + " = " + myMap[key]);
}
}