CanvasRenderingContext2D.beginPath() 是 Canvas 2D API 通过清空子路径列表开始一个新路径的方法。 当你想创建一个新的路径时，调用此方法。
语法
void ctx.beginPath();
示例
使用 beginPath 方法
这是一段受用 beginPath 方法的简单的代码片段。
HTML
<canvas id="canvas"></canvas>
JavaScript
var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");
// First path
ctx.beginPath();
ctx.strokeStyle = 'blue';
ctx.moveTo(20,20);
ctx.lineTo(200,20);
ctx.stroke();
// Second path
ctx.beginPath();
ctx.strokeStyle = 'green';
ctx.moveTo(20,20);
ctx.lineTo(120,120);
ctx.stroke();
修改下面的代码并在线查看 canvas 的变化：
Playable code
<canvas id="canvas" width="400" height="200" class="playable-canvas"></canvas>
<div class="playable-buttons">
<input id="edit" type="button" value="Edit" />
<input id="reset" type="button" value="Reset" />
</div>
<textarea id="code" class="playable-code" style="height:200px">
// First path
ctx.beginPath();
ctx.strokeStyle = 'blue';
ctx.moveTo(20,20);
ctx.lineTo(200,20);
ctx.stroke();
// Second path
ctx.beginPath();
ctx.strokeStyle = 'green';
ctx.moveTo(20,20);
ctx.lineTo(120, 120);
ctx.stroke();</textarea>
var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");
var textarea = document.getElementById("code");
var reset = document.getElementById("reset");
var edit = document.getElementById("edit");
var code = textarea.value;
function drawCanvas() {
ctx.clearRect(0, 0, canvas.width, canvas.height);
eval(textarea.value);
}
reset.addEventListener("click", function() {
textarea.value = code;
drawCanvas();
});
edit.addEventListener("click", function() {
textarea.focus();
})
textarea.addEventListener("input", drawCanvas);
window.addEventListener("load", drawCanvas);
规范描述
浏览器兼容性
| Feature |
Chrome |
Firefox (Gecko) |
Internet Explorer |
Opera |
Safari |
| Basic support |
(Yes) |
(Yes) |
(Yes) |
(Yes) |
(Yes) |
| Feature |
Android |
Chrome for Android |
Firefox Mobile (Gecko) |
IE Mobile |
Opera Mobile |
Safari Mobile |
| Basic support |
(Yes) |
(Yes) |
(Yes) |
(Yes) |
(Yes) |
(Yes) |
参见