Question

我正在使用的代码应该使图像square.png移动到光标。但是，代码无法运行。

我试图在代码中查找拼写错误和错误。

package main

import "fmt"

func main() {
    // Arguments
    arr := []string{"foo", "bar", "baz", "bee", "feo", "boo", "bak"}
    combinations := make([][]string, 0)
    k := 4
    n := len(arr)

    // Execution starts from here
    if k > n {
        panic("invalid requirement")
    }

    pos := make([]int, k) // this variable is used to plot the unique combination of elements

    // initialize an array with first ever plotting possitions
    i := 0
    c := k
    for c > 0 {
        c--
        pos[i] = c
        i++
    }
    combinations = append(combinations, getCombination(arr, pos, k))

    // Let's begin the work
    x := 0
    ctr := 1 // counter is use to calculate total iterations
    for pos[x] < n-(x+1) {
        ctr++
        pos[x]++

        combinations = append(combinations, getCombination(arr, pos, k))

        if pos[x] == n-(x+1) && x+1 < k {
            x++
            i := x
            s := pos[x] + 1
            for i > 0 {
                i--
                s++
                pos[i] = s
            }

            // continue to next index
            continue
        }

        x = 0

    }

    fmt.Println("total # iterations: --> ", ctr)

    fmt.Println(combinations, "\ntotal # combinations: ", len(combinations))

}

func getCombination(arr []string, pos []int, k int) []string {
    combination := make([]string, k)
    for i, j := k-1, 0; i >= 0; i, j = i-1, j+1 {
        combination[j] = arr[pos[i]]
    }
    return combination
}

这是来自html文档中的脚本标签之间。

应该在鼠标指针所在的位置绘制正方形，但是根据Chrome开发工具，变量“ X”和“相似Y”在“加载”函数中无法识别。

Answer 1

正如@eepascarello所说，您正在尝试访问超出范围的变量。您可以将similarX和similarY变量移出mousemove事件的范围之外

var canvas = document.createElement('canvas');
canvas.width = 800;
canvas.height = 600;
document.body.appendChild(canvas);

//possible you want to set these to something besides 0
var similarX = 0;
var similarY = 0;

document.addEventListener('mousemove',function(event){

    similarX = event.clientX;
    similarY = event.clientY;
    document.getElementById('body').innerHTML = "x:" + similarX + ", y:" + similarY;
})
var square = new Image();
square.src = 'square.png';

window.addEventListener('load' , start);

var c = canvas.getContext('2d');
function start() {
    c.fillStyle = 'green';
    c.fillRect = 10, 10, 30, 30;
    c.drawImage(square,similarX , similarY);

    window.requestAnimationFrame(start)
}
document.body.appendChild(canvas);

请注意，这不会为您提供在mousemove上重新定位矩形的功能，但是它将使您能够无错误地进行加载。要更新mousemove，您可能需要做一些事情，例如在start()事件结束时致电mousemove；

为什么我的JavaScript代码中的变量不能正常工作？

1 个答案: