nomilo/assets/scripts/add-form-row.js

function templateString(text, args) {
    for (const argName in args) {
        text = text.replace(`{${argName}}`, args[argName]);
    }

    return text;
}

function addFormRow(templateName) {
    const allRows = document.querySelectorAll(`[data-new-item-template="${templateName}"]`);
    const templateElement = allRows[0];
    const nextId = allRows.length + 1;

    const newItem = templateElement.cloneNode(true);

    newItem.querySelectorAll('[data-new-item-skip]')
        .forEach(node => node.remove());

    // Reset form fields
    newItem.querySelectorAll('input')
        .forEach(input => { input.value = '' });

    newItem.querySelectorAll('textarea')
        .forEach(input => { input.value = '' });

    // Template attributes
    const templatedAttrNodes = newItem.querySelectorAll('[data-new-item-template-attr]');
    for (const node of templatedAttrNodes) {
        const attributes = node.dataset.newItemTemplateAttr.split(/\s/);
        for (const attribute of attributes) {
            const templatedString = node.getAttribute(`data-template-${attribute}`);
            node.setAttribute(attribute, templateString(templatedString, {i: nextId}));
        }
    }

    // Template content
    const templatedNodes = newItem.querySelectorAll('[data-new-item-template-content]');
    for (const node of templatedNodes) {
        const templatedString = node.dataset.newItemTemplateContent;
        node.innerHTML = templateString(templatedString, {i: nextId})
    }

    allRows[allRows.length - 1].insertAdjacentElement('afterend', newItem);
}

function setUpAddFormRow() {
    const buttons = document.querySelectorAll('button[data-new-item]');

    for (const button of buttons) {
        button.addEventListener('click', () => addFormRow(button.dataset.newItem))
    }

}

document.addEventListener('DOMContentLoaded', setUpAddFormRow);