OOP JavaScript對象繼承（父/子）

Question

你好，我正在使用Javascript OOP，我無法讓它工作。我想通過孩子從另一個對象（父母）調用函數。這是我的「類」代碼：

function Unit(_x, _y, _speed) { 
    this.x = _x; 
    this.y = _y; 
    this.dx = _speed; 
    this.dy = _speed; 
    this.gravity = 0; 
} 
Unit.prototype.apply_gravity = function() { 
    this.gravity+=global_gravity; 
    this.y+=this.gravity; 
} 
Unit.prototype.render = function() { 
    context.drawImage(images[0], canvas_screen.x+this.x, canvas_screen.y+this.y); 
} 

function Character() { 
} 

Character.inheritsFrom(Unit); 

我希望能夠調用的函數：「apply_gravity」，並從角色對象這樣的「渲染」：

var character = new Character(100,100,5); 
character.render(); 

Answer 1

替換：

Character.inheritsFrom(Unit); 

有：

Character.prototype = new Unit(0,0,0); // or whatever defaults if you want them 

硒e這jsFiddle Example