JavaScript: For loop to build multidimensional array automatically

You were getting close. As long as you only need to test for the 4 conditions you set up as regex this should work fine. Basically, its just checking what level you are on and either pushing or popping an array off a stack to build the structure you want.

EDIT: I cleaned up code so it wouldn't pollute your scope as much. I also changed your regex a little, some were necessary some were just trying to anticipate data changes (i.e. no space after value or lists going higher than 9).

EDIT2: I also noticed that you were trying to do something with the content so I gave you a way to nest by a property of an object that way you can have useful information along with the nested "labels".

EDIT3: Added a print function to help you test the issue you were having and fixed a bug where jumping from a higher level to more than one level below would incorrectly just decrease one level. You'll see we break apart the content so that it can be nested by labels, then recombine them as you wish during output. Here it's just logging but of course could just as easily be appending html tags to a document.

var autoNest = function(list, prop) {

    var regex1 = /[a-z]\.\s?/,
        regex2 = /[0-9]+\.\s?/,
        regex3 = /\([a-z]\)\.\s?/,
        regex4 = /\([0-9]+\)\.\s?/;

    var getLevel = function(text) {
        if (regex1.test(text)) {
            return 0;
        }    
        if (regex2.test(text)) {
            return 1;        
        }
        if (regex3.test(text)) {
            return 2;
        }
        if (regex4.test(text)) {
            return 3;
        }
        throw new Error('Unexpected content');
    };

    var peek = function(arr) {
        return arr[arr.length - 1];
    };

    var result = [];
    var stack = [result];    
    var lastLevel = 0;

    list.forEach(function(obj) {
        var value = prop ? obj[prop] : obj;
        var currentLevel = getLevel(value);
        var arr = peek(stack);
        if (currentLevel > lastLevel) {
            var next = [];
            arr.push(next);
            stack.push(next);
        } else if (currentLevel < lastLevel) {
            var diff = lastLevel - currentLevel;
            for (var i = 0; i < diff; i++) {
                stack.pop();
            }
        }
        arr = peek(stack);
        arr.push(obj);
        lastLevel = currentLevel;
    });
    return result;
};

$('.elem b').each(function() {
    var label = $(this).text();
    var content = $(this).parent().text();
    items.push({
        label: label,
        content: content
    });
});

function printArray(items, level) {
    level = level || 0;
    items.forEach(function(item) {
        if (Array.isArray(item)) {
            printArray(item, level + 1);
        } else {
            var output = '';
            for (var i = 0; i < level; i++) {
                output += '  ';
            }
            output += item.label + ' ' + item.content;
            console.log(output);
        }
    });
}

var nested = autoNest(items, 'label');
printArray(nested);