Onresize for div elements?

Question

Visual Studio highlighted my onresize attribute of my div tag, and says that it isn\'t a valid attribute for HTML5. Is this true? What should I use

Answer 1

Currently all major browser doesn't support a resize event for html-element's, just for the window object.

What you can to is to intercept the user interaction to build your own listener, like this:

function detectResize(_element)
{
    let promise = {};
    let _listener = [];

    promise.addResizeListener = function(listener)
    {
        if(typeof(listener) != "function") { return; }
        if(_listener.includes(listener)) { return; };

        _listener.push(listener);
    };

    promise.removeResizeListener = function(listener)
    {
        let index = _listener.indexOf(listener);
        if(index >= 0) { _listener.splice(index, 1); }
    };

    let _size = { width: _element.clientWidth, height: _element.clientHeight };

    function checkDimensionChanged()
    {
        let _currentSize = { width: _element.clientWidth, height: _element.clientHeight };
        if(_currentSize.width != _size.width || _currentSize.height != _size.height)
        {
            let previousSize = _size;
            _size = _currentSize;

            let diff = { width: _size.width - previousSize.width, height: _size.height - previousSize.height };

            fire({ width: _size.width, height: _size.height, previousWidth: previousSize.width, previousHeight: previousSize.height, _element: _element, diff: diff });
        }

        _size = _currentSize;
    }

    function fire(info)
    {
        if(!_element.parentNode) { return; }
        _listener.forEach(listener => { listener(info); });
    }


    let mouseDownListener = event =>
    {

        let mouseUpListener = event => 
        {
            window.removeEventListener("mouseup", mouseUpListener);
            window.removeEventListener("mousemove", mouseMoveListener);
        };

        let mouseMoveListener = event =>
        {
            checkDimensionChanged();
        };

        window.addEventListener("mouseup", mouseUpListener);
        window.addEventListener("mousemove", mouseMoveListener);
    };

    _element.addEventListener("mousedown", mouseDownListener);

    window.addEventListener("resize", event =>
    {
        checkDimensionChanged();
    });

    return promise;
}

How to use it:

document.addEventListener("DOMContentLoaded", event =>
{
    let textarea = document.querySelector("textarea");
    let detector = detectResize(textarea);

    let listener = info => { console.log("new width: ", info.width, "  new height: ", info.height); };
    detector.addResizeListener(listener);
});

html:

css:

html, body
{
    height: 100%;
    box-sizing: border-box;
    overflow: hidden;
    margin: 0px;
}

textarea
{
    resize: both;

    width: 96px;
    height: 112px;

    width: 100%;
    height: 100%;

    border: 1px solid black;
}