Check the first line of a file using fileReader in javascript

Question

I have files that I need to check if the first line in the CSV file has a header or not. If it does it will have the word 'symbol' first, if not it will not. So I am going to use this as the criteria for finding the header.

However using fileReader() I am not finding a way to do this? I am familiar with checking for objects however working with the file itself is eluding me.

There are tutorials online for using fileReader() but not that I found do this, can anyone provide some guidance?

guest271314 · Accepted Answer · 2016-10-07 04:16:31Z

2

You can use FileReader.prototype.readAsText(), String.prototype.split() with parameter \n, then check if first element in resulting array contains word "symbol"

document.querySelector("input[type=file]")
.onchange = function(e) {
  var reader = new FileReader();
  reader.onload = function(event) {
    var text = event.target.result;
    var arr = text.split(/\n/).filter(Boolean);
    if (/symbol/.test(arr[0])) {
      console.log("symbol found", arr[0]);
    }
  }
  reader.readAsText(e.target.files[0]);
}

<input type="file">

answered Oct 7, 2016 at 4:16

guest271314

1

Sign up to request clarification or add additional context in comments.

1 Comment

guest271314 Over a year ago

@illcrx For example, you can download gist.githubusercontent.com/anonymous/… , then select file at stacksnippets to check if `"symbol" is found at header of file

Collectives™ on Stack Overflow

Check the first line of a file using fileReader in javascript

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related