JavaScript lets textarea support the TAB key method

This example describes the way JavaScript lets textarea support the TAB key. Share to everyone for your reference. The implementation methods are as follows:

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HTMLTextAreaElement.prototype.getCaretPosition = function () {//return The caret position of the textarea return this.se Lectionstart; }; HTMLTextAreaElement.prototype.setCaretPosition = function (position) {//change caret position of textarea Lectionstart = position; This.selectionend = position; This.focus (); }; HTMLTextAreaElement.prototype.hasSelection = function () {//if the TEXTAREA has selection then return True if (This.selec Tionstart = = This.selectionend) {return false;} else {return true;}}; HTMLTextAreaElement.prototype.getSelectedText = function () {//return The selection text return this.value.substring ( This.selectionstart, This.selectionend); }; HTMLTextAreaElement.prototype.setSelection = function (start, end) {//change the selection area of the textarea This.sele Ctionstart = start; This.selectionend = end; This.focus (); }; var textarea = document.getElementsByTagName (' textarea ') [0]; Textarea.onkeydown = function (event) {//support tab on TextareA if (Event.keycode = = 9) {//tab was pressed var newcaretposition; newcaretposition = textarea.getcaretposition () + "". L Ength; Textarea.value = textarea.value.substring (0, Textarea.getcaretposition ()) + "" + textarea.value.substring ( Textarea.getcaretposition (), textarea.value.length); Textarea.setcaretposition (newcaretposition); return false; } if (Event.keycode = = 8) {//backspace if textarea.value.substring (Textarea.getcaretposition ()-4, Textarea.getcaretposition ()) = = "") {//it ' s tab space Var newcaretposition; Newcaretposition = Textarea.getcaretposition ()-3; Textarea.value = textarea.value.substring (0, Textarea.getcaretposition ()-3) + textarea.value.substring ( Textarea.getcaretposition (), textarea.value.length); Textarea.setcaretposition (newcaretposition); } if (Event.keycode = n) {//left arrow var newcaretposition; if (textarea.value.substring textarea.getcaretposition () -4, textarea.getcaretposition () = = "") {//it ' s a tab space newcaretposition = TEXTAREA.GETCARetposition ()-3; Textarea.setcaretposition (newcaretposition); } if (Event.keycode = n) {//right arrow var newcaretposition; if (textarea.value.substring textarea.getcaretposition ( + 4, textarea.getcaretposition ()) = = "") {//it ' s a tab space newcaretposition = textarea.getcaretposition () + 3; Textarea.setcaretposition (newcaretposition); } } }

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