HTMLImageElement.decode()

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句法
用法注意事项
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decode() 方法在 HTMLImageElement interface returns a Promise that resolves when the image is decoded and it is safe to append the image to the DOM. This can be used to initiate loading of the image prior to attaching it to an element in the DOM (or adding it to the DOM as a new element), so that the image can be rendered immediately upon being added to the DOM. This, in turn, prevents the rendering of the next frame after adding the image to the DOM from causing a delay while the image loads.

句法

var promise = HTMLImageElement.decode();

参数

None.

返回值

A Promise which is resolved once the image data is ready to be used.

异常

EncodingError: DOMException indicating that an error occurred while decoding the image.

用法注意事项

One potential use case for decode() : when loading very large images (for example, in an online photo album), you can present a low resolution thumbnail image initially and then replace that image with the full-resolution image by instantiating a new HTMLImageElement , setting its source to the full-resolution image's URL, then using decode() to get a promise which is resolved once the full-resolution image is ready for use. At that time, you can then replace the low-resolution image with the full-resolution one that's now available.

范例

The following example shows how to use the decode() method to control when an image is appended to the DOM. Without a Promise -returning method, you would add the image to the DOM in a load event handler, such as by using the img.onload event handler, and by handling the error in the error event's handler.

const img = new Image();
img.src = 'nebula.jpg';
img.decode()
.then(() => {
  document.body.appendChild(img);
})
.catch((encodingError) => {
  // Do something with the error.
})

规范

规范	状态	注释
HTML 实时标准 The definition of 'decode()' in that specification.	实时标准	初始定义。

浏览器兼容性

The compatibility table in this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request. 更新 GitHub 上的兼容性数据

	桌面						移动
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
`decode()`	Chrome 64	Edge ≤79	Firefox 68	IE ?	Opera Yes	Safari 11.1	WebView Android 64	Chrome Android 64	Firefox Android 68	Opera Android ?	Safari iOS 11.3	Samsung Internet Android 9.0

图例

完整支持
兼容性未知 ?

元数据

最后修改： Sep 26, 2019

在此页

句法

参数

返回值

异常

用法注意事项

范例

规范

浏览器兼容性

图例

相关话题