Summary of common tools and functions of JavaScript (browser environment)

/**
  * file to base64
  * @param {*} file file object
  * @param {*} callback
  */
export const fileToDataURL = (file, callback) => {
 let freader = new FileReader();
 (file);
  = function (e) { callback(); }
}

/**
  * blob stream converted to base64
  * @param {*} blob blob object
  * @param {*} callback
  */
export const blobToDataURL = (blob, callback) => {
 let freader = new FileReader();
 (blob);
  = function (e) { callback(); }
}

/**
  * Base64 converted to blob
  * @param {*} dataurl base64
  */
export const dataURLtoBlob = (dataurl) => {
 let arr = (','),
  mime = arr[0].match(/:(.*?);/)[1],
  bstr = atob(arr[1]),
  n = ,
  u8arr = new Uint8Array(n);
 while (n--) {
  u8arr[n] = (n);
 }
 return new Blob([u8arr], { type: mime });
}

/**
  * Convert base64 to file, IE lower version is incompatible
  * @param {*} dataurl base64
  * @param {*} filename filename
  */
export const dataURLtoFile = (dataurl, filename) => {
 let arr = (','),
  mime = arr[0].match(/:(.*?);/)[1],
  bstr = atob(arr[1]),
  n = ,
  u8arr = new Uint8Array(n);
 while (n--) {
  u8arr[n] = (n);
 }
 return new File([u8arr], filename, { type: mime });
}

/**
  * Image url is converted to base64
  * @param {*} url Picture url
  * @param {*} callback
  * @param {*} outputFormat image format
  */
export const imgUrlToDataURL = (url, callback, outputFormat) => {
  let canvas = ('canvas'),
    ctx = ('2d'),
    img = new Image;
   = 'Anonymous';
   = url + "?timeStamp=" + new Date().getTime();
   = function () {
     = ;
     = ;
    // (img, 0, 0);
    (this, 0, 0, , );
    let dataURL = (outputFormat || 'image/png');
    // (this, dataURL);
    callback && callback(dataURL)
    canvas = null;
  };
}

export function getViewportSize() {
 let w = 0;
 let h = 0;
 if () {
  w = 
  h = 
 } else if ( && ) {
  w = 
  h = 
 } else if ( && ) {
  w = 
  h = 
 }
 return { w, h }
}

const ua = ()

// Is it WeChat or notexport const isWx = () => (/MicroMessenger/i) == 'micromessenger'

// Is it ipadexport const isIpad = () => ('ipad') > -1

// Is it an iphoneexport const isIphone = () => ('iphone os') > -1

// Is it ucexport const isUc = () => ('ucweb') > -1

// Is it windows pcexport const isWindows = () => ('windows') > -1

// Is it androidexport const isAndroid = () => ('android') > -1 || ('adr') > -1

// Is it iosexport const isIos = () => /(iphone|ipod|ipad|ios)/(ua)

// Is it a qq browserexport const isQq = () => ('mqqbrowser') > -1 && (' qq') < 0

// Is it a built-in browser for QQ?export const isQQInstalled = () => (' qq') > -1 && ('mqqbrowser') < 0

// Turn on full screenexport function launchFullscreen(element) {
 element = element || 
 if () {
  ()
 } else if () {
  ()
 } else if () {
  ()
 } else if () {
  ()
 }
}

// Turn off full screenexport function exitFullscreen() {
 if () {
  ()
 } else if () {
  ()
 } else if () {
  ()
 } else if () {
  ()
 }
}

/**
  * @param {*} number Distance from the top of the page
  * @param {*} time time required to scroll Unit ms
  */
const scrolling = (number = 0, time) => {
  if (!time) {
     =  = number;
    return number;
  }
  // Set the interval time of the cycle. The smaller the value, the higher the consumption performance.  const spacingTime = 20;
  // Calculate the number of cycles  let spacingInex = time / spacingTime; 
  // Get the current scroll bar position  let nowTop =  + ; 
  // Calculate the distance for each slide  let everTop = (number - nowTop) / spacingInex;

  let scrollTimer = setInterval(() => {
    if (spacingInex > 0) {
      spacingInex--;
      ScrollTop(nowTop += everTop);
    } else {
      clearInterval(scrollTimer); // Clear the timer    }
  }, spacingTime);
};

// Scroll to a position 500px from the top of the page. The animation time is 300ms// scrolling(500, 300);

// Use H5's scrollIntoView method, which is a function in an experiment. It is incompatible with IE 8 or below, Safari 6 or below, and Safari on iOS 5 or below.const scrollToAnchor = (anchorName) => {
  if (anchorName) {
    // Find the anchor point    let anchorElement = (anchorName);
    // If the anchor point of the corresponding id exists, jump to the anchor point    if (anchorElement) {
      ({
        behavior: 'auto', // Define the animation transition effect, one of "auto" or "smooth".  Default is "auto"        block: 'start', // Define the alignment of the vertical direction, one of "start", "center", "end", or "nearest".  Default is "start"        inline: 'nearest', // Define the alignment of the horizontal direction, one of "start", "center", "end", or "nearest".  Default is "nearest"      });
    }
  }
}