Include JavaScript file in HTML won't work as <script … />

Question

I have two files in a folder :

main.html
main.js

The main.js as follows:

function revertNum(num){
    var strNum = new String(num);
    var strArr = strNum.split();
    var result = '';
    for(var i = strArr.length - 1; i > 0; i--){
        result += strArr[i];
    }
    return result;
}
var x = revertNum(32132);
console.log(x);

The main.html as follows:

<html>
    <head>
        <meta charset="utf-8" />
        <script src="main.js"></script>
    </head>
    <body>
    </body>
</html>

I expected console of browser will show reverse of 32132, but it only show SRC of main.js file.

Here is the output

What do you mean 'it only show SRC of main.js file'

Andrew Li
– Andrew Li

2016-06-21 16:22:19 +00:00
Commented Jun 21, 2016 at 16:22 — Andrew Li
– Andrew Li, Commented Jun 21, 2016 at 16:22

KevBot · Accepted Answer · 2016-06-21 16:25:41Z

6

You are not actually adding anything to your result. You are logging a line, but it is an empty string.

That being said... try this instead for reversing a string inside of main.js. It is so much more simple and relieves the function of all that code.

function revertNum(num) {
  return String(num).split('').reverse().join('');
}
var x = revertNum(32132);
console.log(x);

answered Jun 21, 2016 at 16:25

KevBot

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Comments

Community · Accepted Answer · 2017-05-23 12:08:26Z

4

There are two errors in your code:

Your split line should give "" as a delimiter: var strArr = str.split("");
Your loop condition should be i >= 0, not i > 0

You're seeing just a blank in the console output because the first error means that strArr is an array with just one element: "32132", and the second error means you stop before processing the last (only) element in the array and return "".

In future, you can find this out for yourself by using the debugger built into your browser:

Add debugger; at the top of main.js -- later, when you're more familiar with the tools, you won't need to do that, but for now it's the easiest way to get you into the debugger
Open a tab
Use the menus to open your "developer tools" (it's F12 or Ctrl+Shift+I or Cmd+Shift+I on most browsers) Now that I see you're using Firefox, from the menus it's Web Developer > Debugger (Ctrl+Shift+S, although Ctrl+Shift+I works to open dev tools, then you just click the Debugger tab).
Open your page. That should switch you to the "Source" or "Sources" or "Debugger" tab in the developer tools with your source code in front of you. (It's "Debugger" in Firefox's built-in tools.)
Use the various tools there to step through the code statement-by-statement, look at the values of variables, etc.

You'll want to find the Developer Tools website for your browser's tools to find out how to use them. This question and its answers have a lot of useful links to those. Firefox's built-in tools are covered here.

edited May 23, 2017 at 12:08

CommunityBot

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answered Jun 21, 2016 at 16:25

T.J. Crowder

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4 Comments

James Thorpe Over a year ago

Also think split could be avoided entirely, and just loop over strNum instead?

mplungjan Over a year ago

split and reverse maks more sense

T.J. Crowder Over a year ago

@JamesThorpe and mplungjan Both good points. I was shooting for minimalist. :-)

James Thorpe Over a year ago

I still like this type of answer - shows why OPs code wasn't working without replacing it with an entirely rewritten option.

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