JSLint mixed spaces and tabs error

Question

I have run the following through JSLint:

$(document).ready(function() {

    /*
        Add paragraph on page load
    */

    // Get all header elements
    var header = document.getElementsByTagName('h1'),
        parent,
        newP,
        text;

    // Loop through the elements
    for (var i=0, m = header.length; i < m; i++) {
        parent = header[i].parentNode;
        newP = document.createElement("p");
        text = document.createTextNode('This paragraph was inserted with JavaScript!');
        newP.appendChild(text);
        // Insert the new P element after the header element in its parent node
        parent.insertBefore(newP, header[i].nextSibling);   
    }

    // so much easier with jQuery!
    //$('.section > h1').after('<p>I am a new paragraph &amp; I have been added to the page with javascript!</p>');

    /*
        Toggle show/hide
    */

    // display show/hide link - hidden by default if JS disabled as functionality is not available
    $('#content > .section > h2 > a').removeClass('hide');

    // hide What's new on page load - all content will be available if JS disabled  
    $('#content > .section > ul').addClass('hide');

    // show/hide content on click event
    $('#content > .section > h2 > a').live('click',function() {

        $('#content > .section > ul').toggle();

        return false;

    });

    /*
        JSON
    */

    var $jsonURL = 'scripts/response.json';

    $.ajax({
        type: 'GET',
        url: $jsonURL,
        dataType: "json",
        success: function(data){

            $.each(data.data, function(i, data){

                var $html = '';

                var $string = '';

                if (data.type == 'comment') {
                    $string = 'file';
                } else {
                    $string = 'workspace';
                }

                $html += '<li class="' + data.type + '">';

                $html += '<strong>New ' + data.type + '</strong> was added to the ' + $string + ' ';

                $html += '<a href="' + data.target + '">' + data.target + '</a> ';

                $html += '<a href="' + data.workspace + '">' + data.workspace + '</a>';

                $html += ' by <a href="#">' + data.user + '</a>'; 

                $html += '</li>';   

                $('#content > .section > ul').append($html);    

            });

        },
        error:function (xhr, ajaxOptions, thrownError){
            alert(xhr.status);
            alert(thrownError);
        }           
    }); 

});

And am getting this error:

Error:

Problem at line 89 character 4: Mixed spaces and tabs.

}

Implied global: $ 1,31,34,37,39,51,57,81, document 1,8,16,17, alert 87,88

Not really sure how to fix?

Answer 1

This error occurs when your indentation uses a combination of both spaces and tabs, for example, {SPACE}{SPACE}{TAB}{SPACE} or {TAB}{SPACE}{TAB}. I'm not really sure why it's an error and not a warning, but the solution is to revisit the line and make sure you only use spaces OR tabs.

The problem with mixing tabs and spaces is you could run into indentation issues when the file is viewed in a different application. For instance, one user may have tabs configured to equal two spaces, another could open the first user's file and see uneven indentation because two spaces plus one tab equals 6 spaces as opposed to 4 in the first's app. Using one or the other ensures better readability of your code.

Interestingly enough, Stack Overflow normalizes tabs into 4 spaces, so copying and pasting your code from here back into JSLint fixes the problem.