blob2str.mjs

import genPm from './genPm.mjs'


/**
 * 前端Blob或input檔案物件轉字串
 *
 * Unit Test: {@link https://github.com/yuda-lyu/wsemi/blob/master/test/blob2str.test.mjs Github}
 * @memberOf wsemi
 * @param {Blob|File} bb 輸入Blob或File
 * @returns {Promise} 回傳Promise，resolve回傳Blob或File的字串，reject回傳錯誤訊息
 * @example
 * need test in browser
 *
 * let strIn = 'abc測試'
 * let b64 = str2b64(strIn)
 * let u8a = b642u8arr(b64)
 * let bb = new Blob([u8a])
 * blob2str(bb)
 *     .then(function(strOut){
 *         console.log(strOut)
 *         // => abc測試
 *     })
 *
 */
function blob2str(bb) {

    //pm
    let pm = genPm()

    //reader
    let reader = new FileReader()

    //onload
    reader.onload = function () {

        //resolve
        pm.resolve(reader.result)

    }

    //onerror
    reader.onerror = function (err) {

        //reject
        pm.reject(err)

    }

    //readAsText
    reader.readAsText(bb)

    return pm
}


export default blob2str