2

我有这个代码工作，但我想改进它：

var c = canvas.getContext("2d"); 
//this is called as an object method I created
var animar = function () {
   var obj = this;//saves the object that called it to later access to its properties
   var counter= 0;
   var animacion = setInterval(function(){
            c.save()
            c.clearRect(0, 0, canvas.width, canvas.height);
            c.rotate(0.1*counter);
            obj.pintar();
            c.restore();
            counter++;

   }, 50);
}

我想使用一个外部函数以备将来使用，但是当我更改我拥有的代码时，存在一个提升问题，我不知道如何在不一直覆盖它的情况下获取 rotar() 函数内部的计数器：

var animar = function () {
    var obj = this;
    var counter= 0;
    var animacion = setInterval(function(){
        rotar(obj)
    }, 50);
}

function rotar (obj) {
    c.save()
    c.clearRect(0, 0, canvas.width, canvas.height);
    c.rotate(0.1*counter);
    obj.pintar();
    c.restore();
    counter++;
}

我知道第一个有效，因为它们是嵌套的，而在第二个示例中则不是。如何在不使用 GLOBAL VARIABLE的情况下为 setInterval 设置计数器？（我的意思是......如果我第二次调用它，它不会从 0 开始。如果我在 animar() 函数中将它设置为 0，它会起作用，但是我需要将它设置为 0在使用计数器或使用具有不同名称的计数器的每个函数中。这两种可能性听起来不太好。）谢谢

4

2 回答 2

3

You just need to put var counter = 0 outside the functions:

var counter;
var animar = function () {
    var obj = this;
    counter = 0; // reset every time before 'animacion'...
    var animacion = setInterval(function(){
        rotar(obj)
    }, 50);
}
function rotar (obj) {
    c.save()
    c.clearRect(0, 0, canvas.width, canvas.height);
    c.rotate(0.1*contador);
    obj.pintar();
    c.restore();
    counter++;
}

Alternatively, if you don't want a global variable, you can follow Walter's answer, or do this:

var animar = function () {
    var obj = this;
    var counter = 0; // new variable every time animar() is called
    var animacion = setInterval(function(){
        rotar(obj, counter);
        counter++;
    }, 50);
}
function rotar (obj, counter) {
    c.save()
    c.clearRect(0, 0, canvas.width, canvas.height);
    c.rotate(0.1*contador);
    obj.pintar();
    c.restore();
}
于 2014-05-13T19:57:30.820 回答
1

make counter scoped inside of your animar object:

var animar = function () {
    var obj = this;
    obj.counter= 0;
    var animacion = setInterval(function(){
        rotar(obj)
    }, 50);
}

function rotar (obj) {
    c.save()
    c.clearRect(0, 0, canvas.width, canvas.height);
    c.rotate(0.1*obj.counter);
    obj.pintar();
    c.restore();
    obj.counter++;
}
于 2014-05-13T20:09:11.763 回答