JavaScript allows Textarea to support the tab button

Source: Internet
Author: User

JavaScript allows Textarea to support the tab button

This example describes how to allow Textarea to support the tab button in JavaScript. Share it with you for your reference. The specific implementation method is as follows:

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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 );

}

}

}

I hope this article will help you design javascript programs.

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