Tab в textarea

textarea-tab.js

$('body').on('keydown', 'textarea', function (event) {
    if (event.keyCode === 9) {
        let v = this.value, s = this.selectionStart, e = this.selectionEnd;
        this.value = v.substring(0, s) + '\t' + v.substring(e);
        this.selectionStart = this.selectionEnd = s + 1;
        return false;
    }
});