Maps (aka Associative Arrays)
This page is under construction. Please come back later.
#!/usr/bin/env node; const Utils = require('./Utils'); const main = async () => { let dictionary = new Map(); console.log("dictionary size: " + dictionary.size); console.log("dictionary is " + (Utils.isEmpty(dictionary) ? "empty" : "not empty")); dictionary.set("apple", "red"); dictionary.set("banana", "yellow"); dictionary.set("cantaloupe", "orange"); dictionary.set("dragonfruit", "red"); dictionary.set("elderberry", "purple"); console.log("dictionary size: " + dictionary.size); console.log("dictionary is " + (Utils.isEmpty(dictionary) ? "empty" : "not empty")); console.log("bananas are " + dictionary.get("banana")); let x = "dragonfruit"; if (dictionary.has(x)) { console.log(x + " are " + dictionary.get(x)); } else { console.log("Can't find " + x); } x = "fig"; if (dictionary.has(x)) { console.log(x + " are " + dictionary.get(x)); } else { console.log("Can't find " + x); } x = "elderberry"; dictionary.delete(x); if (dictionary.has(x)) { console.log(x + " are " + dictionary.get(x)); } else { console.log("Can't find " + x); } console.log(Utils.mapToString(dictionary)); } main().catch( e => { console.error(e) } );
Output
$ node Maps1.js
dictionary size: 0
dictionary is not empty
dictionary size: 5
dictionary is not empty
bananas are yellow
dragonfruit are red
Can't find fig
Can't find elderberry
{"apple" => "red", "banana" => "yellow", "cantaloupe" => "orange", "dragonfruit" => "red"}
#!/usr/bin/env node; const Utils = require('./Utils'); const main = async () => { let planetDiameters = new Map([ ["Mercury", 4879], ["Venus", 12103], ["Earth", 12756], ["Mars", 6794], ["Jupiter", 142985], ["Saturn", 120534], ["Uranus", 51115], ["Neptune", 49534], ["Pluto", 2374], ["Ceres", 946], ["Eris", 2326], ["Makemake", 1430] ]); for (let planet of planetDiameters.keys()) { console.log(planet + " has a diameter of " + planetDiameters.get(planet) + " km"); } } main().catch( e => { console.error(e) } );
Output
$ node Maps2.js
Mercury has a diameter of 4879 km
Venus has a diameter of 12103 km
Earth has a diameter of 12756 km
Mars has a diameter of 6794 km
Jupiter has a diameter of 142985 km
Saturn has a diameter of 120534 km
Uranus has a diameter of 51115 km
Neptune has a diameter of 49534 km
Pluto has a diameter of 2374 km
Ceres has a diameter of 946 km
Eris has a diameter of 2326 km
Makemake has a diameter of 1430 km
Questions
- {{Who's on first?}}
- {{Who's on second?}}
- {{Who's on third?}}
Projects
More ★'s indicate higher difficulty level.
References
- [[JavaScript Language Reference]], Mozilla Developer Network
- [[Mozilla Developer Network]]
- Download [[node.js]]
- [[w3schools.com]]