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事情是我有一個JS類,並且想要創建一個n-ary方法到它的原型(Whisp.prototype.draw),所以它不會一遍又一遍地實例化。我什麼瀏覽器控制檯告訴我是JS原型設計n-ary方法
Uncaught TypeError: w.draw is not a function
我可能誤解了一些有關JS原型,所以這裏是代碼的相關部分:
// Random generators
function randomInt(min, max)
{
return Math.floor(Math.random() * (max - min)) + min;
}
// Whisp object + its methods
var WHISP_TURN_CAP = 10, WHISP_WANDER_CAP = 2, WHISP_SIZE = 2,
WHISP_COUNT = 4;
var Whisp = function(position)
{
this.rotation = [];
this.position = position;
for (var i = 0; i < 3; i++)
this.rotation.push(randomInt(-WHISP_TURN_CAP, WHISP_TURN_CAP))
this.rotation.push(1)
}
Whisp.prototype.wander = function()
{
var angle;
for (var i = 0; i < 3; i++)
{
angle = randomInt(-WHISP_WANDER_CAP, WHISP_WANDER_CAP+1);
while (Math.abs(this.rotation[i] + angle) > WHISP_TURN_CAP)
angle = randomInt(-WHISP_WANDER_CAP, WHISP_WANDER_CAP+1);
this.rotation[i] += angle;
this.position = matrixProduct(this.position, i, this.rotation[i]);
}
};
Whisp.prototype.draw = function(center)
{
context.setFill('#60FF55');
context.fillOval(
center[0]+this.position[0]-WHISP_SIZE,
center[1]+this.position[1]-WHISP_SIZE,
center[0]+this.position[0]+WHISP_SIZE,
center[1]+this.position[1]+WHISP_SIZE
);
};
// Generate actual whisps
var whisps = [];
for (var i = 0; i < WHISP_COUNT; i++)
whisps.push(new Whisp([800,400,0,1]));
// Update function (drawing onto canvas)
var canvas = $('#backgroundCanvas')[0], context = canvas.getContext('2d');
function update()
{
for (var w in whisps)
{
w.draw([800,450]);
w.wander();
}
console.log('update();');
window.setTimeout(update, 20);
}
var whisps = [];
for (var i = 0; i < WHISP_COUNT; i++)
whisps.push(new Whisp([800,400,0,1]));
// Update function (drawing onto canvas)
var canvas = $('#backgroundCanvas')[0], context = canvas.getContext('2d');
function update()
{
for (var w in whisps)
{
w.draw([800,450]);
w.wander();
}
console.log('update();');
window.setTimeout(update, 20);
}
update();
它的所有包裹在$(文件)。就緒(function(){...})。感謝您的答案:)。
ohh,不知道,認爲它像其他語言一樣工作(數組元素被選入w),非常感謝:) –
@KuboMotýľ如果你不關心IE8(你使用的是畫布,所以我假設不)你可以使用[Array.prototype.forEach()](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/forEach) –