JavaScript boolean 问题

Question

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已关闭 10 年前。

所以我正在用 javascript 创建游戏，并且尝试创建 Debug模式，但是当我创建变量 debugVariable 并将其设置为 boolean 值时

var debugVariable = new Boolean();

无论我做什么，它在某种程度上读起来都是真实的。首先这是完整的代码块

 var debugVariable = new Boolean();
function debuggCheckBox()
{
    if(debugVariable){ debugVariable = false;}
    else {debugVariable = true;}
}

function testNumber1()
{
    var num1 = Math.floor(Math.random() * 11);
    var num2 = Math.floor(Math.random() * 3);
    var link = "GAME 2";
    var answer = prompt('LEVEL 1: What is ' + num1 + " * " + num2 +"?");
    if (!answer || answer == ""){
        testNumber1();
    }
    else if (num1 * num2 == answer)
    {
        alert('Correct');
    }
    else if (num1 * num2 != answer)
    {
        alert('Incorrect');
        testNumber1();
    }
}
testNumber1();
function testNumber2()
{
    var num1 = Math.floor(Math.random() * 21);
    var num2 = Math.floor(Math.random() * 13);
    var answer = prompt('LEVEL 2: What is ' + num1 + " * " + num2 +"?");
    if (num1 * num2 == answer)
    {
        alert('Correct');
        ++monstersCaught;
        reset();
        ++level;
    }
    else if (num1 * num2 != answer)
    {
        alert('Incorrect');
        testNumber2();
    }
}
function testNumber3()
{
    var num1 = Math.floor(Math.random() * 31);
    var num2 = Math.floor(Math.random() * 23);
    var answer = prompt('LEVEL 3: What is ' + num1 + " * " + num2 +"?");
    if (num1 * num2 == answer)
    {
        alert('Correct');
        ++monstersCaught;
        ++level;
        reset();
    }
    else if (num1 * num2 != answer)
    {
        alert('Incorrect');
        testNumber3();
    }
}

//checking if canvas is supported
function checkCanvasSupported(){
  var element = document.createElement('canvas');
  return !!(element.getContext && element.getContext('2d'));
}
//if canvas not supported then alert user
if (!checkCanvasSupported()){
    alert('Sorry cavas isn\'t supported by your internet browser!');
}

// Create the canvas
var canvas = document.createElement("canvas");
var ctx = canvas.getContext("2d");
canvas.width = 512;
canvas.height = 480;
document.body.appendChild(canvas);

// Background image
var bgReady = false;
var bgImage = new Image();
bgImage.onload = function () {
    bgReady = true;
};
bgImage.src = "images/background.png";

// Hero image
var heroReady = false;
var heroImage = new Image();
heroImage.onload = function () {
    heroReady = true;
};
heroImage.src = "images/hero.png";

// Monster image
var monsterReady = false;
var monsterImage = new Image();
monsterImage.onload = function () {
    monsterReady = true;
};
monsterImage.src = "images/monster.png";

// Game objects
var hero = {
    speed: 256 // movement in pixels per second
};
var monster = {};
var monster1 = {};
var monster2 = {};
var monstersCaught = 0;
var level = 1;

// Handle keyboard controls
var keysDown = {};

addEventListener("keydown", function (e) {
    keysDown[e.keyCode] = true;
}, false);

addEventListener("keyup", function (e) {
    delete keysDown[e.keyCode];
}, false);

// Reset the game when the player catches a monster
var reset = function () {
    hero.x = canvas.width / 2;
    hero.y = canvas.height / 2;
};

var reset0 = function () {
    hero.x = canvas.width / 2;
    hero.y = canvas.height / 2;
    // Throw the monster somewhere on the screen randomly
    monster.x = 32 + (Math.random() * (canvas.width - 64));
    monster.y = 32 + (Math.random() * (canvas.height - 64));
}

var reset1 = function () {
    hero.x = canvas.width / 2;
    hero.y = canvas.height / 2;

    // Throw the monster somewhere on the screen randomly
    monster1.x = 32 + (Math.random() * (canvas.width - 64));
    monster1.y = 32 + (Math.random() * (canvas.height - 64));
};

var reset2 = function () {
    hero.x = canvas.width / 2;
    hero.y = canvas.height / 2;

    // Throw the monster somewhere on the screen randomly
    monster2.x = 32 + (Math.random() * (canvas.width - 64));
    monster2.y = 32 + (Math.random() * (canvas.height - 64));
};

// Update game objects
var update = function (modifier) {
    if (38 in keysDown) { // Player holding up
        hero.y -= hero.speed * modifier;
        if(hero.y < 0){
            reset();
        }
    }
    if (40 in keysDown) { // Player holding down
        hero.y += hero.speed * modifier;
        if(hero.y > canvas.height){
        reset();

        }
    }
    if (37 in keysDown) { // Player holding left
        hero.x -= hero.speed * modifier;
        if(hero.x < 0){
            reset();
        }
    }
    if (39 in keysDown) { // Player holding right
        hero.x += hero.speed * modifier;
        if(hero.x > canvas.width){
            reset();
        }
    }
    // Are they touching?
    if (
        hero.x <= (monster.x + 32)
        && monster.x <= (hero.x + 32)
        && hero.y <= (monster.y + 32)
        && monster.y <= (hero.y + 32)
    ) {
        ++monstersCaught;
        reset0();
    }
    else if (
        hero.x <= (monster1.x + 32)
        && monster1.x <= (hero.x + 32)
        && hero.y <= (monster1.y + 32)
        && monster1.y <= (hero.y + 32)
    ) {
        ++monstersCaught;
        reset1();
    }
    else if (
        hero.x <= (monster2.x + 32)
        && monster2.x <= (hero.x + 32)
        && hero.y <= (monster2.y + 32)
        && monster2.y <= (hero.y + 32)
    ) {
        ++monstersCaught;
        reset2();
    }
    if (monstersCaught == 5){
        testNumber2();
    }
    else if (monstersCaught == 10){
        testNumber3();
    }
};

// Draw everything
var render = function () {
    if (bgReady) {
        ctx.drawImage(bgImage, 0, 0);
    }

    if (heroReady) {
        ctx.drawImage(heroImage, hero.x, hero.y);
    }

    if (monsterReady) {
        ctx.drawImage(monsterImage, monster.x, monster.y);
        ctx.drawImage(monsterImage, monster1.x, monster1.y);
        ctx.drawImage(monsterImage, monster2.x, monster2.y);
    }
    // Score
    ctx.fillStyle = "rgb(250, 250, 250)";
    ctx.font = "24px Verdana";
    ctx.textAlign = "left";
    ctx.textBaseline = "top";
    ctx.fillText("Score: " + monstersCaught, 32, 32);

    ctx.fillStyle = "rgb(250, 250, 250)";
    ctx.font = "24px Verdana";
    ctx.textAlign = "right";
    ctx.textBaseline = "top";
    ctx.fillText("Level: " + level, 400, 32);

    ctx.fillStyle = "rgb(250, 250, 250)";
    ctx.font = "24px Verdana";
    ctx.textAlign = "center";
    ctx.textBaseline = "top";
    if(debugVariable = true)
    {
        var coords = 'Co-ords(' + hero.x + "," + hero.y + ')';
    } else {
        coords = "";
    }
    ctx.fillText(coords , 100, 200);

    ctx.fillStyle = "rgb(250, 250, 250)";
    ctx.font = "24px Verdana";
    ctx.textAlign = "center";
    ctx.textBaseline = "top";
    ctx.fillText("Debug: " + debugVariable, 100, 100);



};

// The main game loop
var main = function () {
    var now = Date.now();
    var delta = now - then;

    update(delta / 1000);
    render();

    then = now;
};

// Let's play this game!
reset();
reset0();
reset1();
reset2();
var then = Date.now();
setInterval(main, 1); // Execute as fast as possible

这里是主要的问题区域(第 1-6 行)

    var debugVariable = new Boolean();
function debuggCheckBox()
{
    if(debugVariable){ debugVariable = false;}
    else {debugVariable = true;}
}

(第 233-270 行)

var render = function () {
    if (bgReady) {
        ctx.drawImage(bgImage, 0, 0);
    }

    if (heroReady) {
        ctx.drawImage(heroImage, hero.x, hero.y);
    }

    if (monsterReady) {
        ctx.drawImage(monsterImage, monster.x, monster.y);
        ctx.drawImage(monsterImage, monster1.x, monster1.y);
        ctx.drawImage(monsterImage, monster2.x, monster2.y);
    }
    // Score
    ctx.fillStyle = "rgb(250, 250, 250)";
    ctx.font = "24px Verdana";
    ctx.textAlign = "left";
    ctx.textBaseline = "top";
    ctx.fillText("Score: " + monstersCaught, 32, 32);

    ctx.fillStyle = "rgb(250, 250, 250)";
    ctx.font = "24px Verdana";
    ctx.textAlign = "right";
    ctx.textBaseline = "top";
    ctx.fillText("Level: " + level, 400, 32);

    ctx.fillStyle = "rgb(250, 250, 250)";
    ctx.font = "24px Verdana";
    ctx.textAlign = "center";
    ctx.textBaseline = "top";
    if(debugVariable = true)
    {
        var coords = 'Co-ords(' + hero.x + "," + hero.y + ')';
    } else {
        coords = "";
    }
    ctx.fillText(coords , 100, 200);

    ctx.fillStyle = "rgb(250, 250, 250)";
    ctx.font = "24px Verdana";
    ctx.textAlign = "center";
    ctx.textBaseline = "top";
    ctx.fillText("Debug: " + debugVariable, 100, 100);



};

以及复选框的 HTML 代码，尽管它根本不执行任何操作

    <!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="utf-8">
        <title>Simple Canvas Game</title>
        <link rel="stylesheet" type="text/css" href="style/style.css" />
    </head>
    <body>
        <script src="js/game.js"></script>
        <input type="checkbox" name="debugOnOff" onclick="debugCheckBox()">
        <a href="game2.html"> GAME 2</a>
    </body>
</html>

Answer 1

它读取 true 的原因是由于这段代码

var debugVariable = new Boolean();
function debuggCheckBox()
{
    if(debugVariable){ debugVariable = false;}
    else {debugVariable = true;}
}

您正在检查 debugVariable != null 是否存在，要访问 Boolean 对象的原始类型，您需要调用 valueOf 方法。

要检查 true 或 false，您应该使用 false 初始化 debugVariable。

var debugVariable = false;
function debuggCheckBox()
{
    debugVariable = !debugVariable;
}