[JavaScript] Detecting Copy and Paste in JavaScript with jQuery

00-user-has-pasted-content.js

/**
 * Determines if the user has pasted content into the textarea.
 *
 * @param    array    keymap    The array of keys that have been pressed.
 * @return   boolean            True if the user is pasting content.
 */
var user_has_pasted_content = function( keymap ) {

	return ( 0 === $.inArray( 17, keymap ) || 0 === $.inArray( 91, keymap ) ) &&
				 1 === $.inArray( 86, keymap );

};

01-detecting-copy-and-paste.js

// Refers to whatever element (such as a textarea) we're watching
var $elem;

$elem.on( 'keydown', function( evt ) {

	 // Log the keys being pressed (looking specifically for CTRL/CMD + V)
	if ( ( 17 === evt.keyCode || 91 === evt.keyCode ) || 86 === evt.keyCode ) {

		// We only add the keycode if it doesn't already exist in the keymap
		if ( -1 === $.inArray( evt.keyCode, keymap ) ) {
			keymap.push( evt.keyCode );
		}

	}

}).on( 'keyup', function() {

	// Check to see if the key combination exists in the keymap
	if ( user_has_pasted_content( keymap ) ) {

		// Do your work here
		// Reset the keymap for the next operation
		keymap = [];

	}

});