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javascript - 用 slider 控制变量

转载 作者:行者123 更新时间:2023-11-30 11:52:10 26 4
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我想用范围 slider 控制可变长度,这样 slider 就可以增加或减少线的长度。

var canvas = document.getElementById('myCanvas');
var context = canvas.getContext('2d');

var slider = document.getElementById("slider");
var length = 450

context.beginPath();
context.moveTo(100, 100);
context.lineTo(length, 100);
context.stroke();


slider.addEventListener("change", function() {
length = slider.value;
})

setInterval(function() {
length = slider.value;

}, 100)
<!DOCTYPE HTML>
<html>
<head>
</head>
<body>
<input id="slider" type="range" min="1" max="578" step="1" value="50" >
<canvas id="myCanvas" width="578" height="200"></canvas>

</body>
</html>

最佳答案

如果你想改变它的长度,你必须重新绘制整条线。这是它如何工作的示例:

var canvas = document.getElementById('myCanvas');
var context = canvas.getContext('2d');

var slider = document.getElementById("slider");
var length = 450

context.beginPath();
context.moveTo(100, 100);
context.lineTo(length, 100);
context.stroke();

slider.addEventListener("change", function() {
length = slider.value;
context.clearRect(0, 0, canvas.width, canvas.height); // Clears the entire canvas
context.beginPath(); // Draw the line with the new length
context.moveTo(100, 100);
context.lineTo(length, 100);
context.stroke();
})

// You didn't need setIntertval.
<!DOCTYPE HTML>
<html>
<head>
</head>
<body>
<input id="slider" type="range" min="1" max="578" step="1" value="50" >
<canvas id="myCanvas" width="578" height="200"></canvas>
</body>
</html>

关于javascript - 用 slider 控制变量,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/39140171/

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