Use JS to operate files (FileReader reads --node's fs)

<input type="file" multiple>

<script>
	window.onload = function(){
		var inpFile = document.querySelector('input[type=file]')
		inpFile.addEventListener('change', function(){
			var reader = new FileReader()
			// Send asynchronous request // 0. Use the readAsText method (read the result as normal text)
			reader.readAsText(this.files[0]) 
			// Result of successful reading: The file has been read successfully (the file read.txt on the computer)
			reader.onload = function(){
    		//After reading, the data is saved in the result property of the object console.log(this.result)//Print: The file has been read successfully }
		})
	}
</script>

window.onload = function(){
		var inpFile = document.querySelector('input[type=file]')
		inpFile.addEventListener('change', function(){
			var reader = new FileReader()
			// Use readAsDataURL (to get base64 encoding)
			reader.readAsDataURL(this.files[0])
			reader.onload = function(){
    		console.log(this.result)
    		//data:text/plain;base64,5bey57uP5oiQ5Yqf6K+75Y+W5paH5Lu2
  			}
		})
	}

window.onload = function(){
		var inpFile = document.querySelector('input[type=file]')
		inpFile.addEventListener('change', function(){
			var reader = new FileReader()
			reader.readAsText(this.files[0])
			var count = 0;
			reader.onloadstart = function(){
				console.log("onloadstart state"+this.readyState)
    			console.log("Start loading")
  			}
  			reader.onloadend = function(){
  				console.log("onloadend state"+this.readyState)
    			console.log("Loading completed")
  			}
  			reader.onprogress = function(){
  				count++;
  				console.log("onprogress state"+this.readyState)
    			console.log("Loading"+count)
  			}
			reader.onload = function(){
    			console.log("The data obtained by onload is "+this.result)
    			console.log("status"+this.readyState)
  			}
  			reader.onerror = function(){
    			console.log('something went wrong')
  			}
  			reader.onerror = function(){
    			console.log('Handle the abort event. This event is triggered when the read operation is interrupted.')
  			}
		})
	}

// 1. Use the require method to load the fs core module var fs = require('fs')
// 2. Read file // The first parameter is the file path to be read // The second parameter is a callback function // Success // data data // error null
// Failed // data undefined no data // error error object fs.readFile('read.txt', function (error, data) {
  // Here you can check if an error occurs by judging error if (error) {
    console.log('Failed to read the file')
  } else {
    console.log(data.toString())
  }
})

var fs = require('fs')
function pReadFile(filePath) {
  return new Promise(function (resolve, reject) {
    fs.readFile(filePath, 'utf8', function (err, data) {
      if (err) {
        reject(err)
      } else {
        resolve(data)
      }
    })
  })
}
pReadFile('./data/a.txt')
  .then(function (data) {
    console.log(data)
    return pReadFile('./data/b.txt')
  })
  .then(function (data) {
    console.log(data)
    return pReadFile('./data/c.txt')
  })
  .then(function (data) {
    console.log(data)
  })

fs.writeFile('read.txt', 'Hello everyone, let me introduce myself to you. I am a file writer.', function (error) {
  if (error) {
    console.log('Write failed')
  } else {
    console.log('Written successfully')
  }
})