JavaScriptはTextareaにtabボタンをサポートさせる方法です.
2984 ワード
本論文の実例は、JavaScriptがTextaaraにtabボタンをサポートさせる方法を説明する.皆さんの参考にしてください.具体的な実現方法は以下の通りです.
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);
}
}
}