我有一个我不知道如何解决的问题，我测试了一些有关如何比较或检查变量是<!DOCTYPE html>
<html>
<body>
<style>
canvas {
background: #eee;
}
</style>
<canvas id="ctx" tabindex=0 width=900 height=500 style="border:1px solid #000000;" onkeypress="movePlayer(event)" onkeyup="keyUp(event)"></canvas>
<script>
var canvas = document.getElementById("ctx");
var ctx = canvas.getContext("2d");
canvas.setAttribute('tabindex', 0);
canvas.focus();
canvas.addEventListener("keydown", movePlayer);
//Maybe I can get a class working?
class Platform {
constructor(x, y, xS, yS, moveBool) {
this.xPos = x;
this.yPos = y;
this.xSize = xS;
this.ySize = yS;
this.moveable = moveBool;
if (this.moveable) {
this.setDirection('right')
}
}
render() {
ctx.save()
ctx.fillStyle = "red";
ctx.fillRect(this.xPos, this.yPos, this.xSize, this.ySize);
ctx.restore()
}
get getX() {
return this.xPos;
}
get getY() {
return this.yPos;
}
get getxSize() {
return this.xSize;
}
get getySize() {
return this.ySize;
}
get getMoveable() {
return this.moveable;
}
setDirection(direction) {
this.direction = direction
}
moveX(speed) {
this.xPos += speed;
}
}
//Platform array:
platformArray = [];
//Platforms:
platform1 = new Platform(100, 350, 200, 10, true);
platformArray.push(platform1);
platform2 = new Platform(300, 200, 200, 10, false);
platformArray.push(platform2);
platform3 = new Platform(400, 300, 200, 10, false);
platformArray.push(platform3);
//Vars:
var x_new = 50;
var y_new = 50;
var isJumping = false;
var isColliding = false;
var speed = 10;
var keys = {
up: false,
right: false,
left: false
};
function movePlayer(event) {
switch (event.keyCode) {
//Right key down:
case 39:
keys["right"] = true;
break;
//Left key down:
case 37:
keys["left"] = true;
break;
//Up key down:
case 38:
keys["up"] = true;
isJumping = true;
break;
}
}
function keyUp(event) {
switch (event.keyCode) {
//Up key up:
case 38:
isJumping = false;
keys["up"] = false;
break;
//Right key up:
case 39:
keys["right"] = false;
break;
//Left key up:
case 37:
keys["left"] = false;
break;
}
}
function boundsIntersect(x1, y1, x2, y2) {
if (x1 > x2 - 50 && x1 < x2 + 200 && y1 < y2 && y1 > y2 - 55) {
return true;
}
return false;
}
function update() {
ctx.clearRect(0, 0, 900, 500);
//Move platforms:
platformArray.forEach(function(platform) {
if (platform.getMoveable) {
if (platform.getX > 0 && platform.getX < 400) {
if (platform.direction === 'right') {
platform.moveX(5);
} else {
platform.moveX(-5);
}
} else if (platform.getX >= 400) {
platform.moveX(-5);
platform.setDirection('left')
} else if (platform.getX <= 0) {
platform.moveX(5);
platform.setDirection('right')
}
}
});
//PLayer movement:
if (keys["up"] && !keys["right"] && !keys["left"]) {
y_new -= speed;
} else if (keys["right"] && !keys["up"]) {
x_new += speed;
} else if (keys["left"] && !keys["up"]) {
x_new -= speed;
} else if (keys["up"] && keys["right"]) {
y_new -= speed;
x_new += speed;
} else if (keys["up"] && keys["left"]) {
y_new -= speed;
x_new -= speed;
}
//Platform intersections:
platformArray.forEach(function(platform) {
if (boundsIntersect(x_new, y_new, platform.getX, platform.getY) && isJumping == false) {
isColliding = true;
y_new -= 10;
} else if (boundsIntersect(x_new, y_new, platform.getX, platform.getY) && isJumping == true) {
isJumping = false;
y_new += 11;
isColliding = true;
} else {
isColliding = false;
}
});
if (y_new < 440 && isJumping == false && isColliding == false) {
y_new += speed;
}
// render platforms
platformArray.forEach(function (platform) {
platform.render()
})
// render player
ctx.save()
ctx.fillStyle = "black";
ctx.beginPath();
ctx.fillRect(x_new, y_new, 50, 50);
//Draw ground:
ctx.beginPath();
ctx.rect(0, 490, 900, 10);
ctx.fillStyle = "green";
ctx.fill();
ctx.restore()
window.requestAnimationFrame(update);
}
window.requestAnimationFrame(update);
</script>
</body>
</html>还是array的信息 >
我已经尝试过了
object问题是，我想知道变量是否确实是console.log({} == []); // return false
console.log({1:"haha"} == {}); // return false
console.log(["haha"] == {}); // retun false
或object的{{1}}原因typeof返回[]。 / p>
{}或
object是否有console.log(isobject({1:"haha"})) // should return true;
console.log(isobject(["haha"])); // should return false;
像上面那样检查console.log(isobject({})) // should return true;
console.log(isobject([])); // should return false;
？
感谢您的任何纠正。
答案 0 :(得分：2)
arr = [1,2,3]
Array.isArray(arr) //应该输出true
对于我会做的对象
obj = {a:1}
Object.keys(obj).length //应该输出1
所以你可以做
Object.keys(obj).length >= 0 //如果obj是obj字面量应为true。
答案 1 :(得分：2)
这会有所帮助。
var a = [], b = {};
console.log(Object.prototype.toString.call(a).indexOf("Array")>-1);
console.log(Object.prototype.toString.call(b).indexOf("Object")>-1);
console.log(a.constructor.name == "Array");
console.log(b.constructor.name == "Object");
还有许多其他方法，但是以上方法在所有浏览器中都向后兼容。
必须参考相关问题：