Javascript

Question

我在 p5.js 中制作一个非常简单的绘图网络应用程序时遇到了错误。错误说它在第 10 行，但我没有看到错误？也许我对数组做错了。

var pixels = [];
var drawing = false;

function setup() {
    createCanvas(windowWidth, windowHeight);
}
function draw() {
    background(0);
    for(var i = pixels.length - 1;i >= 0;i++) {
        pixels[i].show();
    }
    if(drawing) {
        var nP = new Pixel(mouseX, mouseY);
        pixels.push(nP);
    }
}

function mousePressed() {
    drawing = true;
}
function mouseReleased() {
    drawing = false;
}

function Pixel(x, y) {
    this.x = x;
    this.y = y;

    this.show = function() {
        push();
        noStroke();
        fill(255);
        rect(this.x, this.y, 10, 10);
        pop();
    }
}

Answer 1

问题在行-

for(var i = pixels.length - 1;i >= 0;i++)

为了向后遍历数组，您需要递减计数器，而不是递增它。所以，正确的循环应该是-

for(var i = pixels.length - 1;i >= 0;i--)

Javascript - Uncaught TypeError: Cannot read property 'show' of undefined

Javascript - Uncaught TypeError: Cannot read property 'show' of undefined

arrays

p5.js