I have a Player class that has some properties like name, id, score etc... and few methods that modify the score property
Over the course of the execution i end up saving few instances of this class to JSON files. Then later on, I import them back into an array called players. In order to retrieve the class' methods in each object in the array, I did the following:
class Player {
constructor(_name,_id) {
this.name = _name;
this.age = _age;
this.score = 0;
}
addScore(x) {this.score += x}
multiplyScore(x) {this.score *= x}
removeScore(x) {this.score -= x}
}
// The function `loadFiles()` returns: [{name:"foo",id:0,score:15},{name:"bar",id:1,score:9}]
const players = loadFiles().map(x => Object.setPrototypeOf(x, Player.prototype));
Normally, when I use the setPrototypeOf() method, it would return an instance of the class I chose with properties values from the targeted object, and then if I do console.log(players[0].constructor.name) it should print out Player except that the objects in players remain exactly the same, the methods aren't added into them and their constructor.name is not Player.
PS: the process works fine if I do this on one object instead of mapping/looping through an array of them.
There is nothing wrong with the code, it is working completely fine.
class Player {
constructor(_name,_id) {
this.name = _name;
this.age = _age;
this.score = 0;
}
addScore(x) {this.score += x}
multiplyScore(x) {this.score *= x}
removeScore(x) {this.score -= x}
}
// The function `loadFiles()` returns: [{name:"foo",id:0,score:15},{name:"bar",id:1,score:9}]
const loadFilesResponse = [{name:"foo",id:0,score:15},{name:"bar",id:1,score:9}];
const players = loadFilesResponse.map(x => Object.setPrototypeOf(x, Player.prototype));
console.log("Score before add: ", players[0].score);
players[0].addScore(3);
console.log("Score after add: ", players[0].score);It's possible that loadFiles doesn't actually returns the expected Object, for example it could be returning a list of promises (a common mistake when dealing with promises).
You have the data, just create objects from that data instead of doing object prototype hackery?
const players = loadFiles().map(p => {
const { name, age, score } = p;
p = new Player(name, age);
p.score = score;
return p;
});
Although extending that constructor a little would make it less work:
class Player {
constructor(name, age, score = 0) {
this.name = name;
this.age = age;
this.score = score;
}
...
}
...
const players = loadFiles().map(p => {
const { name, age, score } = p;
return = new Player(name, age, score);
});
This you can call the constructor with two or three arguments, and if you call it with two the score argument will simply default to 0. Much easier.