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aspect.js
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67 lines (56 loc) · 1.35 KB
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'use strict';
class Point {
#x;
#y;
constructor(x, y) {
const errors = Point.validate(x, y);
if (errors.length > 0) {
const cause = new AggregateError(errors, 'Validation');
throw new RangeError('Bad coordinates', { cause });
}
this.#x = x;
this.#y = y;
}
static validate(x, y) {
const errors = [];
if (!Number.isFinite(x)) errors.push(new TypeError(`Invalid x: ${x}`));
if (!Number.isFinite(y)) errors.push(new TypeError(`Invalid y: ${y}`));
return errors;
}
move(x, y) {
this.#x += x;
this.#y += y;
}
clone() {
return new Point(this.#x, this.#y);
}
toString() {
return `(${this.#x}, ${this.#y})`;
}
}
const aspect = (target, methodName, { before, after }) => {
const method = target[methodName];
target[methodName] = function (...args) {
before?.apply(this, args);
const result = method.apply(this, args);
after?.call(this, result, ...args);
return result;
};
};
aspect(Point.prototype, 'move', {
before(x, y) {
console.log(`Before move: ${this.toString()} moving by (${x},${y})`);
},
after() {
console.log(`After move: ${this.toString()}`);
},
});
aspect(Point.prototype, 'clone', {
after(result) {
console.log(`After clone: ${result.toString()}`);
},
});
// Usage
const p1 = new Point(10, 20);
const c1 = p1.clone();
c1.move(-5, 10);