Irgendwie sind alle Beispiele, obwohl sie gut funktionieren, überkompliziert:
- Sie verwenden
new Array(), was ein Overkill (und ein Overhead) für ein einfaches assoziatives Array (AKA-Wörterbuch) ist.
- Die besseren benutzen
new Object(). Funktioniert gut, aber warum all diese zusätzlichen Eingaben?
Diese Frage ist mit "Anfänger" gekennzeichnet. Machen wir es uns einfach.
Die überaus einfache Möglichkeit, ein Wörterbuch in JavaScript zu verwenden oder "Warum hat JavaScript kein spezielles Wörterbuchobjekt?":
// create an empty associative array (in JavaScript it is called ... Object)
var dict = {}; // huh? {} is a shortcut for "new Object()"
// add a key named fred with value 42
dict.fred = 42; // we can do that because "fred" is a constant
// and conforms to id rules
// add a key named 2bob2 with value "twins!"
dict["2bob2"] = "twins!"; // we use the subscript notation because
// the key is arbitrary (not id)
// add an arbitrary dynamic key with a dynamic value
var key = ..., // insanely complex calculations for the key
val = ...; // insanely complex calculations for the value
dict[key] = val;
// read value of "fred"
val = dict.fred;
// read value of 2bob2
val = dict["2bob2"];
// read value of our cool secret key
val = dict[key];
Ändern wir nun die Werte:
// change the value of fred
dict.fred = "astra";
// the assignment creates and/or replaces key-value pairs
// change value of 2bob2
dict["2bob2"] = [1, 2, 3]; // any legal value can be used
// change value of our secret key
dict[key] = undefined;
// contrary to popular beliefs assigning "undefined" does not remove the key
// go over all keys and values in our dictionary
for (key in dict) {
// for-in loop goes over all properties including inherited properties
// let's use only our own properties
if (dict.hasOwnProperty(key)) {
console.log("key = " + key + ", value = " + dict[key]);
}
}
Das Löschen von Werten ist ebenfalls einfach:
// let's delete fred
delete dict.fred;
// fred is removed, the rest is still intact
// let's delete 2bob2
delete dict["2bob2"];
// let's delete our secret key
delete dict[key];
// now dict is empty
// let's replace it, recreating all original data
dict = {
fred: 42,
"2bob2": "twins!"
// we can't add the original secret key because it was dynamic,
// we can only add static keys
// ...
// oh well
temp1: val
};
// let's rename temp1 into our secret key:
if (key != "temp1") {
dict[key] = dict.temp1; // copy the value
delete dict.temp1; // kill the old key
} else {
// do nothing, we are good ;-)
}