JAVASCRIPT

js tab in textarea

document.querySelector('#textarea').addEventListener('keydown', e => {
	if ( e.key === 'Tab' && !e.shiftKey ) {
		// execCommand operations are "Cmd|Ctrl+Z"-able
      	// note: execCommand is deprecated and may not work in the future
		document.execCommand('insertText', false, "	");
		e.preventDefault();
		return false;
	}
});

add tab to textarea javascript

document.getElementById('textbox').addEventListener('keydown', function(e) {
  if (e.key == 'Tab') {
    e.preventDefault();
    var start = this.selectionStart;
    var end = this.selectionEnd;

    // set textarea value to: text before caret + tab + text after caret
    this.value = this.value.substring(0, start) +
      "	" + this.value.substring(end);

    // put caret at right position again
    this.selectionStart =
      this.selectionEnd = start + 1;
  }
});

tab adds tab textarea javascript

$(document).delegate('#textbox', 'keydown', function(e) {
  var keyCode = e.keyCode || e.which;

  if (keyCode == 9) {
    e.preventDefault();
    var start = this.selectionStart;
    var end = this.selectionEnd;

    // set textarea value to: text before caret + tab + text after caret
    $(this).val($(this).val().substring(0, start)
                + "	"
                + $(this).val().substring(end));

    // put caret at right position again
    this.selectionStart =
    this.selectionEnd = start + 1;
  }
});