resize_table.js

const table = document.getElementById('resize_table_row');
const cols = table.querySelectorAll('div.col-lg');

const createResizableColumn = function (col, resizer) {
    // Track the current position of mouse
    let x = 0;
    let w = 0;

    const mouseDownHandler = function (e) {
        // Get the current mouse position
        x = e.clientX;

        // Calculate the current width of column
        const styles = window.getComputedStyle(col);
        w = parseInt(styles.width, 10);

        // Attach listeners for document's events
        document.addEventListener('mousemove', mouseMoveHandler);
        document.addEventListener('mouseup', mouseUpHandler);
        resizer.classList.add('resizing');
    };

    const mouseMoveHandler = function (e) {
        // Determine how far the mouse has been moved
        const dx = e.clientX - x;

        // Update the width of column
        col.style.width = `${w + dx}px`;
    };

    // When user releases the mouse, remove the existing event listeners
    const mouseUpHandler = function () {
        document.removeEventListener('mousemove', mouseMoveHandler);
        document.removeEventListener('mouseup', mouseUpHandler);
        resizer.classList.remove('resizing');
    };

    resizer.addEventListener('mousedown', mouseDownHandler);
};

const cols_len = cols.length;
[].forEach.call([].slice.call(cols,0,-1), function (col) {
    col.style.width = `${100/cols_len}%`;
});

[].forEach.call([].slice.call(cols,0,-1), function (col) {
    // Create a resizer element
    const resizer = document.createElement('div');
    resizer.classList.add('resizer');

    // Set the height
    //resizer.style.height = `${table.offsetHeight/2}px`;
    resizer.style.height = "100%";

    // Add a resizer element to the column
    col.appendChild(resizer);

    // Will be implemented in the next section
    createResizableColumn(col, resizer);
});