ArrayBuffer
:用来表示通用的、固定长度的原始二进制数据缓冲区。它是一个字节数组,通常在其他语言中称为 byte array
TypedArray
:它是一个指定特定元素类型(Int8Array)的统称,详情见 MDNlet buffer = new ArrayBuffer(8); // 8个字节的ArrayBuffer
console.log(buffer.byteLength); // 8字节
const int8Array = new Int8Array(buffer);
console.log(int8Array.length); // 元素的长度 1个字节占用8个位
console.log(int8Array.buffer===buffer); // true
let int16Array = new Int16Array(buffer);
console.log(int16Array.length); // 4字节
DataView
:可以从 ArrayBuffer
对象中读写多种数值类型的底层接口使用它时不用考虑不同平台的字节序(大小端)问题let buffer = new ArrayBuffer(2); //2个字节的ArrayBuffer
console.log(buffer.byteLength); //2
let dataView = new DataView(buffer);
console.log(dataView.buffer === buffer); // true
dataView.setInt8(0, 1);
dataView.setInt8(1, 2);
console.log(dataView.getInt8(0)); //1
console.log(dataView.getInt8(1)); //2
console.log(dataView.getInt16(0)); // 取一个二个字节(16位的整数) [0,0,0,0,0,0,0,1,0,0,0,0,0,0,1,0] = 258
let debug = {name:'limy'};
let str = JSON.stringify(debug);
console.log(str); // {"name":"limy"}
let blob = new Blob([str],{type:'application/json'});
console.log('blob.size',blob.size); // 15
//同样一个blob可以被读成各种类型
function readBlob(blob,type){
return new Promise(function(resolve){
let reader = new FileReader();
reader.onload = function(event){
resolve(event.target.result);
}
switch(type){
case 'ArrayBuffer':
reader.readAsArrayBuffer(blob);
break;
case 'DataURL'://二进制数据转成可读的字符串 base64字符串
reader.readAsDataURL(blob);
break;
case 'Text':
reader.readAsText(blob,'utf-8');
break;
default:
break;
}
});
}
readBlob(blob,'ArrayBuffer').then(result=>{
console.log(result); // 一个arraybuffer对象,可以通过浏览器看下
});
readBlob(blob,'DataURL').then(result=>{
console.log(result); // base64格式 data:application/json;base64,eyJuYW1lIjoibGlteSJ9
});
readBlob(blob,'Text').then(result=>{
console.log(result); // {"name":"limy"}
});
const a = document.createElement('a')
a.href = window.URL.createObjectURL(blob) // 生成的这个url可以放到 src中完成图片显示
a.target = '_blank'
a.download = fileName
document.body.appendChild(a)
a.click()
document.body.removeChild(a)
let encodedData = window.btoa("Hello, world"); // "SGVsbG8sIHdvcmxk"
let decodedData = window.atob(encodedData); // "Hello, world"
function bufferToBlob(buffer){
return new Blob([buffer])
}
function blobToBuffer(blob) {
const reader = new FileReader();
reader.onload = function(e) { // 这里是异步结果不能直接获取
console.log(reader.result)
}
reader.readAsArrayBuffer(blob);
}
function blobToDataURL(blob){
return window.URL.createObjectURL(blob)
}
function dataURLtoBlob(dataurl) {
var arr = dataurl.split(','),
mime = arr[0].match(/:(.*?);/)[1],
bstr = atob(arr[1]),
n = bstr.length,
u8arr = new Uint8Array(n);
while (n--) {
u8arr[n] = bstr.charCodeAt(n);
}
return new Blob([u8arr], {
type: mime
});
}
function arrayBufferToBase64(bytes) {
let binary = ''
const len = bytes.byteLength
for (var i = 0; i < len; i++) {
binary += String.fromCharCode(bytes[ i ])
}
return window.btoa(binary)
}
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