Emmet Expansion Challenge

To tackle the Emmet expansion challenge, we can create a function in JavaScript that processes a given abbreviation string. The function will need to parse the abbreviation, handle nesting, manage repetitions, and include classes, IDs, and text nodes as specified. Recursion is a great fit for managing nested structures. We’ll begin by defining a core function, expandEmmet, that takes an abbreviation string as input, breaks it down into components, and constructs the corresponding HTML. The function will utilize a stack or recursion to handle nested elements and will use regular expressions to identify the patterns in the abbreviations.

function expandEmmet(abbreviation) {
    const result = [];
    const stack = [];
    let currentElement = '';
    
    for (let char of abbreviation) {
        if (char === '>') {
            if (currentElement) {
                stack.push(currentElement);
            }
            currentElement = '';
        } else if (char === '*') {
            const repeatCount = parseInt(abbreviation.slice(abbreviation.indexOf('*') + 1));
            const repeatedElements = result.slice(-1)[0];
            for (let i = 1; i < repeatCount; i++) {
                result.push(repeatedElements);
            }
            break; 
        } else if (char === '{') {
            const text = abbreviation.slice(abbreviation.indexOf('{') + 1, abbreviation.indexOf('}'));
            result.push(currentElement + text.replace('$', result.length + 1));
            currentElement = '';
        } else {
            currentElement += char;
        }
    }
    
    while (stack.length) {
        const parent = stack.pop();
        result.push(`<${parent}>${result.join('')}`);
    }

    return result.join('');
}

// Example usage:
console.log(expandEmmet('ul>li*5{Item $}'));
console.log(expandEmmet('div#main>ul.nav>li.item*3{Item $}'));

In this implementation, we iterate through the abbreviation, processing characters one at a time. We handle the various symbols that denote structure and repeat counts while allowing insertion of text nodes. Edge cases, such as invalid abbreviations, can be dealt with in the parsing step by adding validation checks to ensure that the characters and structure comply with the expected Emmet format. This approach will give you a solid foundation for expanding Emmet abbreviations into full HTML code, along with room to optimize and refine your logic further.