JavaScript ban back key (Backspace) instance code

Source: Internet
Author: User

This article describes the JavaScript ban back key (Backspace) instance code, the need for friends can refer to the

Copy code code as follows:

function Banbackspace (e) {

var ev = e | | window.event;//Get Event Object

var obj = Ev.target | | ev.srcelement;//Get Event Source

var t = Obj.type | | Obj.getattribute (' type ');//Get Event Source Type

Get the event type as a criterion

var vreadonly = obj.readonly;

var vdisabled = obj.disabled;

Handling Undefined values

Vreadonly = (Vreadonly = = undefined)? False:vreadonly;

vdisabled = (vdisabled = = undefined)? true:vdisabled;

When you hit the BACKSPACE key, the event source type is a password or a single line, multi-line text,

And the ReadOnly property is true or the disabled property is true, the backspace key is invalidated

var Flag1 = Ev.keycode = 8 && (t = = "password" | | t = = "text" | | | = = "TEXTAREA") && (vreadonly = = True | | vdisabled = = true);

When the BACKSPACE key is hit, the event source type is not a password or a single line or multi-line text, the BACKSPACE key is invalidated

var Flag2 = Ev.keycode = = 8 && t!= "password" && t!= "text" && t!= "textarea";

Judge

if (Flag2 | | flag1) return FALSE

}

Disable backspace key for Firefox, Opera

document.onkeypress = Banbackspace;

Disable backspace key for IE, Chrome

Document.onkeydown = Banbackspace;

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