FileReader 是Web API 的一部分,它允许网页上的应用程序异步读取用户计算机上的文件内容。当你在 JavaScript 环境中遇到 "FileReader is not defined" 的错误时,这通常意味着你试图在非浏览器环境中(如 Node.js 或某些服务端 JavaScript 框架如 Next.js 的服务端渲染部分)使用 FileReader,而这些环境并不支持 FileRea...
img 转为base64（转）方法一:canvas function getBase64Image(img) { var canvas = docume...
JavaScript中FileReader对象的使用有哪些常见问题? 是因为FileReader是浏览器内置的对象,不是全局变量。它主要用于在Web应用程序中读取文件内容。要使用FileReader对象,需要先创建一个实例,然后通过调用其方法来读取文件。 FileReader对象的主要方法包括: readAsText(file):以文本形式读取文件内容。 readAsDataURL(file):以Data...
Thefor( in )loop is being misused as it struggles with the length property, which is not a Blob Object. This issue arises becausefor( in )iterates through all enumerable object properties, rather than just "own properties". Please refer to the documentation for more information. You...
correctPath(isWindows: boolean, path: string): string Defined in lib/common/lib/config-file-reader.ts:76 Parameters isWindows: boolean path: string Returns string Static expandUserHome expandUserHome(path: string): string Defined in lib/common/lib/config-file-reader.ts:60 Par...
JavaScript function previewFiles() { var preview = document.querySelector('#preview'); var files = document.querySelector('input[type=file]').files; function readAndPreview(file) { // Make sure `file.name` matches our extensions criteria if ( /\.(jpe?g|png|gif)$/i.test(file.name) ...
JavaScript functionpreviewFile(){constpreview=document.querySelector('img');constfile=document.querySelector('input[type=file]').files[0];constreader=newFileReader();reader.addEventListener("load",function(){// convert image file to base64 stringpreview.src=reader.result;},false);if(file){reader...
Returns the file's contents. This property is only valid after the read operation is complete, and the format of the data depends on which of the methods was used to initiate the read operation.
The readAsBinaryString method is used to start reading the contents of the specified Blob or File. When the read operation is finished, the readyState becomes DONE, and the loadend is triggered. At that time, the result attribute contains the raw binary
只有在收到数据后才调用函数drawMap()或任何其他函数，因此在reader.onload回调中，如果您想稍后访问此...