D'une manière ou d'une autre, tous les exemples, bien qu'ils fonctionnent bien, sont trop compliqués:
- Ils utilisent
new Array(), qui est une surpuissance (et une surcharge) pour un tableau associatif simple (dictionnaire AKA).
- Les meilleurs utilisent
new Object(). Fonctionne bien, mais pourquoi toute cette frappe supplémentaire?
Cette question est étiquetée "débutant", alors simplifions les choses.
La manière la plus simple d'utiliser un dictionnaire en JavaScript ou "Pourquoi JavaScript n'a pas d'objet de dictionnaire spécial?":
// 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];
Modifions maintenant les valeurs:
// 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]);
}
}
La suppression de valeurs est également très simple:
// 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 ;-)
}