What if you want to encapsulate this logic into its own function, and return the contents of the file? 注意：在遍历时把 var fileReader = new FileReader(); 放到了循环之外,会导致了 Uncaught InvalidStateError: Failed to execute 'readAsDataURL' on 'FileReader': The object is already busy reading Blobs.错误，这个FileReader应该对应于每一个读取的文件都需要重新new一个。 El Lenguaje Unificado de Modelado (UML, Unified Modeling Language) es un lenguaje gráfico para visualizar, construir y documentar los artefactos de un sistema con gran cantidad de software. You can read the specs of the FileReader object here. This time, I used forkJoin. Jest's modulePaths option makes it possible. Each flatMap arguments were former methods return values. This method can return one of these values. 최근 FileReader 를 사용할 일이 생겨 File API 를 정리 해보고자 한다. If you need a solution for the main thread that "reads like" a synchronous API, i.e. 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. This method can return one of these values. Try wrapping your onload function in another function. getting return values from load events or waiting till finished, "In complete darkness we are all the same, it is only our knowledge and wisdom that separates us, don't let your eyes deceive you.". S_OK. The FileReader object lets web applications asynchronously read the contents of files (or raw data buffers) stored on the user's computer, using File or Blob objects to specify the file or data to read. Remove properties from objects (JavaScript). Reading Files Using The HTML5 FileReader API. file-uploader.service.ts The FileReader.onload property contains a event handler executed when the load event is fired, when content read with readAsArrayBuffer, readAsBinaryString, readAsDataURL or readAsText is available. FileReader.onload I thought only DOM event like Button.onclick could be used by fromEvent. If the Promise is rejected the FileReader will abort and, in this case, return a custom DOMException but you can reject with whatever you like. Syntax var file = instanceOfFileReader.result Value FileReader.abort(): This method aborts or stops the read operation and makes the readyState value to DONE. FileReader.onloadend // The handler for the progress event. The execution time of this method is after the onload method; Methods of FileReader. Learn the Methods of javaScript filereader. Wrapping the result of a FileReader in a Promise allows us to await the result of our readUploadedFileAsText function and expect a string. Example 1: convert file into base64 in javascript function getBase64(file) { return new Promise((resolve, reject) => { const reader = new FileReader(); reader.readAs In this blog post you are going to learn how to use the FileReader API . (Why) is this negative outlook on the concept of philosophy misguided? You can even pass a callback function that will be executed once the file is read. Here's an example onchange handler we could pass to a

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