Exercise from a TypeScript course:
Create a map using TypeScript Generics. The key is always a string.
The value can be a string or a number. It has to work with both types.
It's got to have the following methods:
- Creating a new key-value pair : setItem(key: string, item: T)
- Retrieving values : getItem(key: string)
- Remove all items : clear()
- Display all key-value items : printMap() "
Here my uncompiled TypeScript code:
// -- THE ACTUAL IMPLEMENTATION --------------------------
class GenericMap < T extends number | string > {
private items: object[]
constructor() {
this.items = [];
}
setItem(key: string, item: T): void {
let tmp = {};
tmp[key] = item;
this.items.push(tmp);
}
getItem(key: string): T {
let ret = null;
for (let i = 0; i < this.items.length; i++) {
let curr = this.items[i];
if (curr[key]) {
return curr[key];
}
}
return null;
}
clear() {
this.items.length = 0;
}
printMap() {
this.items.forEach((item) => {
let key: string[] = Object.keys(item);
console.log('{ "' + key[0] + '": ', item[key[0]], '}');
});
}
}
// ------- JUST TESTING --------------------
const numb = new GenericMap < number > ();
numb.setItem('alpha', 7);
numb.setItem('beta', 14);
numb.printMap();
numb.clear();
numb.printMap();
const strMap = new GenericMap < string > ();
strMap.setItem('color', 'Blue');
strMap.setItem('height', '54 cm');
strMap.printMap();
// ---------------------------------------------The compiled code as a live-demo:
class GenMap {
constructor() {
this.items = [];
}
setItem(key, item) {
let tmp = {};
tmp[key] = item;
this.items.push(tmp);
}
getItem(key) {
let ret = null;
for (let i = 0; i < this.items.length; i++) {
let curr = this.items[i];
if (curr[key]) {
return curr[key];
}
}
return null;
}
clear() {
this.items.length = 0;
}
printMap() {
this.items.forEach((item) => {
let key = Object.keys(item);
console.log('{ "' + key[0] + '": ', item[key[0]], '}');
});
}
}
const numb = new GenMap();
numb.setItem('alpha', 7);
numb.setItem('beta', 14);
numb.printMap();
numb.clear();
numb.printMap();
const strMap = new GenMap();
strMap.setItem('color', 'Blue');
strMap.setItem('height', '54 cm');
strMap.printMap();It works fine. But I guess there a better ways to solve these exercise.
Especially my getItem-method has become rather long.
Has someone an idea to solve the exercise in a more elegant way?
What do you think about my idea of storing objects within an array?
Looking forward to reading your answers and comments.
