JavaScript讓Textarea支持tab按鍵的方法

 　　本文實例講述了JavaScript讓Textarea支持tab按鍵的方法。分享給大家供大家參考。具體實現方法如下：

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 HTMLTextAreaElement.prototype.getCaretPosition = function () { //return the caret position of the textarea return this.selectionStart; }; HTMLTextAreaElement.prototype.setCaretPosition = function (position) { //change the caret position of the textarea this.selectionStart = position; this.selectionEnd = position; this.focus(); }; HTMLTextAreaElement.prototype.hasSelection = function () { //if the textarea has selection then return true if (this.selectionStart == 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.selectionStart = 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() + " ".length; 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 a 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 == 37){ //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 == 39){ //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); } } }

　　希望本文所述對大家的javascript程序設計有所幫助。