Wechat applet determines the file format of URL

There are two ways of thinking

The first way of thinking

example ： http://www.example.com:8888/group1/M00/00/85/rBITVV_Qh2mAdwB0cSE513.jpg
1. lookup URL the last one “.” The index of
2. Intercept all characters following this index ( Here is the suffix )
3. Get the suffix to match and judge whether it is in a certain format

//  Whether the file is a picture  ( Method 1 )
var isImg = function (url) {
    
  // Get the last . The location of 
  var index = url.lastIndexOf(".")
  // To obtain the suffix 
  var ext = url.substring(index + 1) // wxs I won't support it substr
  //  Judge 
  return ['png', 'jpg', 'jpeg', 'bmp', 'gif', 'webp', 'psd', 'svg', 'tiff'].indexOf(ext.toLowerCase()) !== -1
}

The second way of thinking

1. take URL use “.” Split into arrays
2. Find the last item in the array ( The last item is the suffix )
3. Get the suffix to judge

//  Method 2 
var isImg2 = function (url) {
    
  // Suffix acquisition 
  let suffix = '';
  //  Get type results 
  let result = '';
  //  Division url Of “.”
  const flieArr = url.split('.');
  //  Get the suffix of the last item in the split array 
  suffix = flieArr[flieArr.length - 1];
  if (suffix != "") {
    
    suffix = suffix.toLocaleLowerCase();
    //  Image format 
    const imglist = ['png', 'jpg', 'jpeg', 'bmp', 'gif']
    //  Match pictures 
    result = imglist.find(function (item) {
    
      return item === suffix
    })
    return result
  }
}