wapp-script.js

var inputText = '._3u328';
var sendBtn = '._3M-N-';

setInterval(function(){
    document.querySelector(inputText).innerText = 'test';
    var event = new Event('input', {
        'bubbles': true,
        'cancelable': true
    });

    document.querySelector(inputText).dispatchEvent(event);
    setTimeout(function(){document.querySelector(sendBtn).click();}, 1)
}, 2000);