I need to check if file name suffix is type JavaScript (JS files end with *.js) for that I use the following code which works

var ext = aa.getName().substr(aa.getName().lastIndexOf('.') + 1);

Now the problem is that if the file is named file2.json I'm still getting true (it's return json) My question is if there a better way to do it i.e. given any file name like file1.xml, file2.js, file3.json or file4.html, it will return true just for file2.

I need to check if file name suffix is type JavaScript (JS files end with *.js) for that I use the following code which works

var ext = aa.getName().substr(aa.getName().lastIndexOf('.') + 1);

Now the problem is that if the file is named file2.json I'm still getting true (it's return json) My question is if there a better way to do it i.e. given any file name like file1.xml, file2.js, file3.json or file4.html, it will return true just for file2.

• javascript
• regex

Share Improve this question Follow edited Aug 6, 2017 at 19:56 louisfischer 2,08422 gold badges2525 silver badges4040 bronze badges asked Aug 6, 2017 at 14:00 Jenny HiltonJenny Hilton 1,40777 gold badges2222 silver badges4242 bronze badges 2

• /.*\.js$/ or /\.js$/ should work, but where do you do this? node or browser? – baao Commented Aug 6, 2017 at 14:03
• @baao - I use it in the browser – Jenny Hilton Commented Aug 6, 2017 at 14:04

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6 Answers 6

Sorted by: Reset to default 3

I believe this can work

function check(str){
    if(str.match(/(\w*)\.js$/) == null){
        console.log('false');
        return false;
    }
    else {
        console.log('true');
        return true;
    }
}
     
check('file1.xml');
check('file2.js');
check('file3.json');
check('file4.html');

let isJS = function(filename) {
    return /\.js$/i.test(filename)
}


console.log(isJS("asd.json")) // false;
console.log(isJS("asdjs"))    // false;
console.log(isJS("asd.js"))   // true;
console.log(isJS("asd.JS"))   // true;

You could check if string ends with .js with the following function:

function isJavascriptFile(str) {
  var regex = /\.js$/;
  var match = str.match(regex);

  return match !== null;
}

According to your code you would use it like this:

var name = aa.getName();
isJavascriptFile(name);

I think for this case better not using regex,

  var arr = [
    'file1.xml',
    'file2.js',
    'file3.json',
    'file4.html'
  ];

  for(var i=0, len=arr.length; i<len; i++){
    if(returnExtension(arr[i]) == 'js') {
      alert('Your file is: ' + arr[i])
    }
  }

  function returnExtension(filename){
    var a = filename.split(".");
    if( a.length === 1 || ( a[0] === "" && a.length === 2 ) ) {
      return "";
    }
    return a.pop();
  }

my working example is here https://jsfiddle/gat8mx7y/

You've to modify your code a little bit, you're almost right:

funciton isJavascriptFile(fileName){
   var ext = fileName.substr(fileName.lastIndexOf('.') + 1);
   if(ext === 'js'){ return true; } 
   return false;
}

if(isJavascriptFile(aa.getName()) ) {
  console.log("file is javascript");
}

 //function GetJSName(){
  var filename="sample.js";
  var name = filename.split('.')[0];
  alert(name);

//};

<script src="https://ajax.googleapis./ajax/libs/jquery/2.1.1/jquery.min.js"></script>