file转base64

 // file转base64
 const getBase64=function(file) {
        return new Promise((resolve, reject) => {
            let reader = new FileReader();
            let fileResult = "";
            reader.readAsDataURL(file);
            //开始转
            reader.onload = function () {
                //这里其实就是需要的base64格式了
                let Result = reader.result;
                //base64数据去头
                let head = Result.indexOf("4") + 2;
                fileResult = Result.substring(head, Result.length - head);
            };
            //转 失败
            reader.onerror = function (error) {
                reject(error);
            };
            //转 结束  咱就 resolve 出去
            reader.onloadend = function () {
                resolve(fileResult);
            };
        });
    },

base64转file

 // base64转file
 const dataURLtoFile=function(dataurl, filename) {
        let arr = `data:image/png;base64,${dataurl}`.split(",")
        let mime = arr[0].match(/:(.*?);/)[1]
        let bstr = window.atob(arr[1])
        let n = bstr.length
        let u8arr = new Uint8Array(n)
        while (n--) {
            u8arr[n] = bstr.charCodeAt(n);
        }
        // 如果需要指定格式可以设置type，如 type: "application/vnd.ms-excel" 表示excel格式blob ;默认为 type: mime 按 MIME 规范编码.
        const blob = new File([u8arr], filename || "file", { type: mime });
        // 如果不需要 formdata 包装,上一步就可以了
        let params = new FormData();
        params.append("file", blob);
        return params;
    },

base64转blob

//base64转blob
const base64ToBlob = function(base64Data) {
	let file = window.atob(fileData.fileData);
        let len = file.length
        // 创建一个存储解码后数据的数组
        let arr = new Uint8Array(len);
        // blob只能接收二进制编码，需要讲base64转为二进制再塞进去
        for (var i = 0; i < len; i++) {
            arr[i] = file.charCodeAt(i);
        }
        let blob = new Blob([arr], {
            type: "application/vnd.ms-excel"
        });
    return blob
};

blob转base64

//blob转base64
const blobToBase64=function(blob) {
        return new Promise((resolve, reject) => {
            const fileReader = new FileReader();
            fileReader.onload = (e) => {
                resolve(e.target.result);
            };
            // readAsDataURL
            fileReader.readAsDataURL(blob);
            fileReader.onerror = () => {
                reject(new Error('blobToBase64 error'));
            };
        });
    }

blob转file

const blobToFile=function(blob){
   return new File([blob], 'name.wav', {type: 'audio/wav'});
}

blob转blobUrl

const blobToBlobUrl=function(blob){
    window.URL = window.URL || window.webkitURL;
	return window.URL.createObjectURL(blob);
}

file转blob

const flieToBlob=function(file){
    return new Promise((resolve, reject) => {
            const fileReader = new FileReader();
            fileReader.onload = (e) => {
                resolve(new Blob([e.target.result], { type: file.type }));
            };
            // readAsDataURL
            fileReader.readAsDataURL(file);
            fileReader.onerror = () => {
                reject(new Error('flieToBlob error'));
            };
        });
}