将blob转成file

利用new File();

function blobToFile(blob, filename, type) {
	return new File([blob], filename, { type })
}

blobToFile('test info', 'test', 'text/plain' )

输出如下

更进一步了解可阅读MDN File - Web API 鎺ュ彛鍙傝€? | MDNMDN Web DocsMDN logoMozilla logo

Blob() - Web API 接口参考 | MDN讲解

将file转换成DataURL

利用URL.createObjectURL()

<input type="file" id="file">
<img id="img">

let img = document.getElementById('img')
let file = document.getElementById('file')
file.onchange = function () {
let imgFile = this.files[0]
img.src = URL.createObjectURL(imgFile)
	img.onload = function () {
		URL.revokeObjectURL(this.src)
	}
}

更进一步了解可阅读 MDN URL.createObjectURL() - Web API 鎺ュ彛鍙傝€? | MDNMDN Web DocsMDN logoMozilla logo 讲解

利用FileReader.readAsDataURL()

let img = document.getElementById('img')
let file = document.getElementById('file')
file.onchange = function (e) {
let imgFile = this.files[0]
let fileReader = new FileReader()
fileReader.readAsDataURL(imgFile)
  fileReader.onload = function () {
  	img.src = this.result
  }
}

更进一步了解可阅读FileReader - Web API 鎺ュ彛鍙傝€? | MDNMDN Web DocsMDN logoMozilla logo简介

将DataURL转成file

function dataURLToFile (dataUrl, fileName) {
const dataArr = dataUrl.split(',')
const mime = dataArr[0].match(/:(.*);/)[1]
const originStr = atob(dataArr[1])
	return new File([originStr], fileName, { type: mime })
}
dataURLToFile('data:text/plain;base64,YWFhYWFhYQ==', '测试文件')
// File {name: '测试文件', lastModified: 1640784525620, lastModifiedDate: Wed Dec 29 2021 21:28:45 GMT+0800 (中国标准时间), webkitRelativePath: '', size: 7, …}

复杂处理方式如下

function dataURLToFile (dataUrl, filename) {
const dataArr = dataUrl.split(',')
const mime = dataArr[0].match(/:(.*);/)[1]
const originStr = atob(dataArr[1])
let n = originStr.length
const u8Arr = new Uint8Array(n)
  while (n--) {
  	u8Arr[n] = originStr.charCodeAt(n)
  }
return new File([u8Arr], filename, { type: mime })
}
dataURLToFile('data:text/plain;base64,YWFhYWFhYQ==', '测试文件')
console.log(dataURLToFile('data:text/plain;base64,YWFhYWFhYQ==','测试文件'));
// File {name: '测试文件', lastModified: 1640784866937, lastModifiedDate: Wed Dec 29 2021 21:34:26 GMT+0800 (中国标准时间), webkitRelativePath: '', size: 7, …}

将canvas转成DataURL

利用canvas.toDataURL()

// html
<input type="file" accept="image/*" id="file">
// js
document.querySelector('#file').onchange = function () {
  canvasToDataURL(this.files[0]).then(res => console.log(res))
 }
function canvasToDataURL (file) {
return new Promise(resolve => {
    const img = document.createElement('img')
    img.src = URL.createObjectURL(file)
    img.onload = function () {
    const canvas = document.createElement('canvas')
    canvas.width = img.width
    canvas.height = img.height
    const ctx = canvas.getContext('2d')
    ctx.drawImage(img, 0, 0)
    resolve(canvas.toDataURL('image/png', 1))
    }
})
}

将DataURL转成canvas

function dataUrlToCanvas (dataUrl) {
return new Promise(resolve => {
    const img = new Image()
    img.src = dataUrl
    img.onload = function () {
    const canvas = document.createElement('canvas')
    canvas.width = this.width
    canvas.height = this.height
    const ctx = canvas.getContext('2d')
    ctx.drawImage(this, 0, 0)
    resolve(canvas)
    }
})
}
const dataUrl = 'data:image/png;base64,iVBORw0KGgoAAAANSUh...'
dataUrlToCanvas(dataUrl)
.then(res => document.body.appendChild(res))

将canvas转成blob

利用canvas.toBlob()

// html
<input type="file" accept="image/*" id="file">
// js
document.querySelector('#file').onchange = function () {
canvasToDataURL(this.files[0])
.then(res => console.log(res))
}
function canvasToDataURL (file) {
return new Promise(resolve => {
  const img = document.createElement('img')
  img.src = URL.createObjectURL(file)
  img.onload = function () {
  const canvas = document.createElement('canvas')
  canvas.width = img.width
  canvas.height = img.height
  const ctx = canvas.getContext('2d')
  ctx.drawImage(img, 0, 0)
  canvas.toBlob(function (e) {
  	resolve(e)
  }, 'image/png', 1)
}
})

将canvas转成file

将canvas转成Blob，然后将Blob转成file即可，可看最开始的文件类型转换流程图。

或将canvas转成dataURL，然后将dataURL转成file即可，可看最开始的文件类型转换流程图。

blob转arrayBuffer

利用
FileReader.readAsArrayBuffer()

function blobToArrayBuffer (blob, callback) {
const reader = new FileReader()
reader.readAsArrayBuffer(blob)
reader.onload = function () {
	callback(this.result)
}
}
let blob = new Blob([1, 2, 3, 4, 5])
blobToArrayBuffer(blob, (arrayBuffer) => { console.log(arrayBuffer) })
// ArrayBuffer(5)

arrayBuffer转blob

利用new Blob()

function arrayBufferToBlob (arrayBuffer, type) {
	return new Blob([arrayBuffer], { type })
}
blobToArrayBuffer(new Blob([1, 2, 3, 4, 5]), (arrayBuffer) => {
console.log(arrayBufferToBlob(arrayBuffer, 'text/plain'))
// Blob {size: 5, type: 'text/plain'}
})

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原文链接：
https://blog.csdn.net/weixin_44116302/article/details/122064841