how to detect copy and paste in javascript?

i have two field one is emailid and another is password in my form. i want to detect that when user reenter the email and password than he should not able to copy the above. he have to write again manually.Just like google forms

回答1:

You could disable ctrl+v combination and right click as well.

for IE, you may tap into following event handlers:

onpaste="return false;" 
oncut="return false;" 
oncontextmenu="return false;" 
oncopy="return false;".

Here is a workaround for all browsers:

function noCTRL(e) {
      var code = (document.all) ? event.keyCode : e.which;
      var ctrl = (document.all) ? event.ctrlKey : e.modifiers & Event.CONTROL_MASK;
      var msg = "Sorry, this functionality is disabled.";
      if (document.all) {
        if (ctrl && code == 86) {
          //CTRL+V
          alert(msg);
          window.event.returnValue = false;
        } else if (ctrl && code == 67) { 
         //CTRL+C (Copy)
          alert(msg);
          window.event.returnValue = false;
        }
      } else {
        if (ctrl == 2) {
          //CTRL key
          alert(msg);
          return false;
        }
      }
    }

In HTML section, your fields would look like:

Email :<input name="email" type="text" value=""/><br/>
Password :<input name="password" type="password" value=""/><br/>
Confirm Email :<input name="email" type="text" value="" onkeydown="return noCTRL(event)"/>    
Confirm Password :<input name="password" type="password" value="" onkeydown="return noCTRL(event)"/>

I don't think user can copy password fields if input type is password

Hope this helps.

Note:

Disabling JavaScript in browser will let users do whatever they want
Always Keep this in mind: respect user's freedom.

回答2:

2020 update

There are copy and paste events you can use to prevent these actions, or to modify the data being copied or pasted. (see the links for browser support)

const elem = document.getElementById('nopaste');

elem.addEventListener('paste', (event) => {
  event.preventDefault();
});

<input type="text" placeholder="can paste"><br>
<input type="text" id="nopaste" placeholder="can not paste">