function Point(x, y) {
this.x = x;
this.y = y;
}
Point.prototype.toString = function () {
return '(' + this.x + ', ' + this.y + ')';
};
var p = new Point(1, 2);
========================================
// 等同于
Point.prototype = {
constructor() {},
toString() {},
toValue() {},
};
class Point {
// ...
}
typeof Point // "function"
Point === Point.prototype.constructor // true