javascript - (切换)函数未定义

Question

我正在尝试使用按钮来打开和关闭 P5 振荡器的音频(因为据我了解，WebAudio API 内容现在需要在浏览器中进行交互才能播放音频)。

在设置之前我有:

var button;

在功能设置中我有:

button = createButton("audio on/off");
button.mousePressed(toggle);
button.position(32, 180);

在功能切换中我有:

if (!playing()) {
    osc.start();
    //playing = true; } else {
    osc.stop();
    //playing = false; }

它一直给我错误消息

Uncaught ReferenceError: toggle is not defined (sketch: line 45)"

为什么我总是收到这个信息？任何帮助将不胜感激。

完整的 sketch.js 代码是:

var button;
var stepX;
var stepY;
let osc; 

function setup() {
  createCanvas(displayWidth, displayHeight);
  noCursor();
  noStroke();
  colorMode(HSB, width, height, 100); 
  reverb = new p5.Reverb();
  delay = new p5.Delay();
  osc = new p5.Oscillator();
  osc.setType('sine');
  reverb.process(osc, 5, 5);
  osc.start();
  // delay.process() accepts 4 parameters:
  // source, delayTime, feedback, filter frequency
  // play with these numbers!!
  delay.process(osc, 0.6, 0.3, 1000);

  // play the noise with an envelope,
  // a series of fades ( time / value pairs )

  var t = 10
  let text = createP("s-p-e-c-t-r-u-m");

  text.position(30, 30);
  text.style("font-family", "monospace");
  text.style("background-color", "#FFFFFF");
  text.style("color", "#F20FD7");
  text.style("font-size", "12pt");
  text.style("padding", "10px");

  let texty = createP("move mouse to control the <br>sine-wave theramin.<br><br>x axis = pitch 30-3000hz<br>y axis = volume quiet-loud)");

  texty.position(32, 80);
  //texty.style("background-color", "#FFFFFF");
  texty.style("font-family", "monospace");
  texty.style("color", "#FFFFFF");
  texty.style("font-size", "10pt");


  button = createButton("audio on/off");
  button.mousePressed(toggle);
  button.position(32, 180);

}

function draw() {
  let pitch = map(mouseX, 0, width, 30, 3000);
  let volume = map(mouseY, 0, height, 1, 0);
  background(200);
  osc.freq(pitch);
  osc.amp(volume);

  stepX = mouseX + 2;
  stepY = mouseY + 2;

  for (var gridY = 0; gridY < height; gridY += stepY) {
    for(var gridX = 0; gridX < width; gridX += stepX) {
      fill(gridX, height - gridY, 100);
      rect(gridX, gridY, stepX, stepY);
    }
  }


function toggle() {
  if (!playing) {
    osc.start();
    playing = true;
  } else {
    osc.stop();
    playing = false;
    }
  }

}

Answer 1

toggle 在 draw 范围内声明:

function draw() {

// [...]

   function toggle() {

       // [...]
   }
}

将其移出draw，即可解决问题:

function draw() {

// [...]
}

function toggle() {

// [...]
}

参见示例:

var button;
var stepX;
var stepY;
let osc; 

function setup() {
    createCanvas(displayWidth, displayHeight);
    noCursor();
    noStroke();
    colorMode(HSB, width, height, 100); 
    reverb = new p5.Reverb();
    delay = new p5.Delay();
    osc = new p5.Oscillator();
    osc.setType('sine');
    reverb.process(osc, 5, 5);
    osc.start();
    // delay.process() accepts 4 parameters:
    // source, delayTime, feedback, filter frequency
    // play with these numbers!!
    delay.process(osc, 0.6, 0.3, 1000);

    // play the noise with an envelope,
    // a series of fades ( time / value pairs )

    var t = 10
    let text = createP("s-p-e-c-t-r-u-m");

    text.position(30, 30);
    text.style("font-family", "monospace");
    text.style("background-color", "#FFFFFF");
    text.style("color", "#F20FD7");
    text.style("font-size", "12pt");
    text.style("padding", "10px");

    let texty = createP("move mouse to control the <br>sine-wave theramin.<br><br>x axis = pitch 30-3000hz<br>y axis = volume quiet-loud)");

    texty.position(32, 80);
    //texty.style("background-color", "#FFFFFF");
    texty.style("font-family", "monospace");
    texty.style("color", "#FFFFFF");
    texty.style("font-size", "10pt");

    button = createButton("audio on/off");
    button.mousePressed(toggle);
    button.position(32, 180);
}

function draw() {
    let pitch = map(mouseX, 0, width, 30, 3000);
    let volume = map(mouseY, 0, height, 1, 0);
    background(200);
    osc.freq(pitch);
    osc.amp(volume);

    stepX = mouseX + 2;
    stepY = mouseY + 2;

    for (var gridY = 0; gridY < height; gridY += stepY) {
        for(var gridX = 0; gridX < width; gridX += stepX) {
            fill(gridX, height - gridY, 100);
            rect(gridX, gridY, stepX, stepY);
        }
    }
}

function toggle() {
    if (!playing) {
        osc.start();
        playing = true;
    } else {
        osc.stop();
        playing = false;
    }
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/p5.js/0.9.0/p5.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/p5.js/0.9.0/addons/p5.sound.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/p5.js/0.9.0/addons/p5.dom.js"></script>