Get value from text file in javascript

Question

I have a javascript variable which I display on my html website, I also have a .txt file which gets a payment value from a .php script. These values are displayed like this 12345 in the .txt file, every amount is raised by 1, so first the .txt file gets 1 then 2 then 3 etc. Now my question is, how do I get the last value from the .txt file and turn my variable value into the value I get, by the last value of the .txt file I mean if the current values in the file is 12345 then the last value is 5, then I want to change the variable in my Javascript to that value 5.

My javascript/html script with the variable and display inside.

<div class="newValue">
        Current value: $<span id="newValueVariable"></span>
</div>

 <script type="text/javascript"> 

        var newValueVariable= 1;
        document.getElementById("newValueVariable").innerHTML = newValueVariable;

</script>

Will 10 be appended after 9 (...8910)? In that case would the "last value" be 0 or 10? — user2570380
– user2570380, Commented Apr 3, 2015 at 23:39
@user2570380 yes 10 will be after 9 then the last value will be 10 — DevLiv
– DevLiv, Commented Apr 3, 2015 at 23:41
So how are you supposed to know how many digits to use at the end? You need to put a delimiter between the values so you can tell. — Barmar
– Barmar, Commented Apr 3, 2015 at 23:42
@Typo do you mean the format of how the numbers are displayed like 123? because if so it doesn't matter as long as it follows, so it could also be like 1 2 3 4 5 6 etc. or 1,2,3,4,5,6 etc. as long as the function still gets the last value of the .txt file in this case 6. — DevLiv
– DevLiv, Commented Apr 3, 2015 at 23:43

Barmar · Accepted Answer · 2015-04-03 23:53:00Z

2

Use AJAX:

var xhr = new XMLHttpRequest;
xhr.open("filename.txt", "GET", true);
xhr.onreadystatechange = function() {
    if (xhr.readyState == 4 && xhr.status == 200) {
        var contents = xhr.responseString;
        // Replace next line with what you actually use to parse the file
        var lastChar = contents.substr(-1, 1);
        document.getElementById("newValueVariable").innerHTML = lastChar;
    }
}
xhr.send();

edited Apr 3, 2015 at 23:53

answered Apr 3, 2015 at 23:47

Barmar

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3 Comments

DevLiv Over a year ago

Thank you very much for the answer, before testing the function, I still need to do the delimiter? if so is it just making a comma or space between the numbers?

Barmar Over a year ago

Yes, you'll need to change the lastChar line to whatever is appropriate for your actual file format.

DevLiv Over a year ago

I have edited my scripts now so it just has to get the value in the text file and not a specific value, can I edit your script in some way to make it work or do I have to do it another way now?

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