This is a function that will be called when pressing tab when writing inside a text area element in html. This will create 4 spaces just like a tab.

presstab.js

$('#textarea').keydown(function (e) {
    var keyCode = e.keyCode || e.which;

    if (keyCode === $.ui.keyCode.TAB) {
        e.preventDefault();

        const TAB_SIZE = 4;

        // The one-liner that does the magic
        document.execCommand('insertText', false, ' '.repeat(TAB_SIZE));
    }
});