javascript 常用函数

将 base64 字符串转换成文件

function base64ToFile (b64Data, contentType) {    contentType = contentType || ''    const sliceSize = 512    const byteCharacters = atob(b64Data)    const byteArrays = []    for (let offset = 0; offset < byteCharacters.length; offset += sliceSize) {      const slice = byteCharacters.slice(offset, offset + sliceSize)      const byteNumbers = new Array(slice.length)      for (let i = 0; i < slice.length; i++) {        byteNumbers[ i ] = slice.charCodeAt(i)      }      const byteArray = new Uint8Array(byteNumbers)      byteArrays.push(byteArray)    }    return new File(byteArrays, 'image.png', { type: contentType })}

打印日志

function _log(info) {    var loggerDom = document.querySelector("#logger");    var loggerTitle = null;    if(!loggerDom) {        loggerDom = document.createElement("div");        loggerDom.id = "logger";        loggerTitle = document.createElement("p");        loggerTitle.innerHTML = "日志标题:";        loggerTitle.style.cssText = "color:blue;font-weight:bold";        loggerDom.appendChild(loggerTitle);        document.querySelector("body").appendChild(loggerDom);    }    var pDom = document.createElement("p");    pDom.innerHTML = new Date().toISOString() + ":<span style='color:red;font-weight:bold;'>" + info + "</span>";    loggerDom.insertBefore(pDom, loggerDom.childNodes[1]);}

显示精确到天的倒计时

/** * 显示精确到天的倒计时 * @param timeStr 日期字符串，格式：2017年04月30日09时00分11秒 * @param currDate 当前时间的 Date 对象 */function showCountdownAccurateToDate (timeStr, currDate) {  const TOTAL_TIME_FOR_SECOND = 1000  const TOTAL_TIME_FOR_MINUTE = TOTAL_TIME_FOR_SECOND * 60  const TOTAL_TIME_FOR_HOUR = TOTAL_TIME_FOR_MINUTE * 60  const TOTAL_TIME_FOR_DAY = TOTAL_TIME_FOR_HOUR * 24  let time = new Date(timeStr.replace(/[年月]/g, '/').replace(/[日秒]/g, ' ').replace(/[时分秒]/g, ':').substring(0, 19)).getTime()  let nowTime = currDate.getTime()  let timeDiff = time - nowTime  let showStr = []  if (time - nowTime > 0) {    let day = parseInt(timeDiff / TOTAL_TIME_FOR_DAY)    let hour = parseInt((timeDiff - day * TOTAL_TIME_FOR_DAY) / TOTAL_TIME_FOR_HOUR)    let minute = parseInt((timeDiff - day * TOTAL_TIME_FOR_DAY - hour * TOTAL_TIME_FOR_HOUR) / TOTAL_TIME_FOR_MINUTE)    let second = parseInt((timeDiff - day * TOTAL_TIME_FOR_DAY - hour * TOTAL_TIME_FOR_HOUR - minute * TOTAL_TIME_FOR_MINUTE) / TOTAL_TIME_FOR_SECOND)    showStr.push(day + '天')    showStr.push(hour + '时')    showStr.push(minute + '分')    showStr.push(second + '秒')    return showStr.join('')  } else {    return timeStr  }}