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]);
    }
}