How to detect keyboard modifier (Ctrl or Shift) through JavaScript

key codes:

shift 16 ctrl 17 alt 18 

your jQuery:

$(document).keydown(function (e) { if (e.keyCode == 18) { alert("ALT was pressed"); } }); 

JavaScript Madness: Keyboard Events

You can use the following:

document.onkeypress = function(evt) { evt = evt || window.event; etv = evt; switch (etv.keyCode) { case 16: // Code to do when Shift presed console.log('Pressed [SHIFT]'); break; case 17: // Code to do when CTRL presed console.log('Pressed [CTRL]'); break; case 32: // Code to do when ALT presed console.log('Pressed [ALT]'); break; } };

I needed a solution for this too, so found some stuff that worked, cleaned it up to be a lot less code, and ES6... JSFiddle link

function isCapsLock(event=window.event) { const code = event.charCode || event.keyCode; if (code > 64 && code < 91 && !event.shiftKey) { return true; } return false; } document.getElementById("text").addEventListener("keypress", event => { const status = document.getElementById("status"); if (isCapsLock(event)) { status.innerHTML = "CapsLocks enabled"; status.style.color = "red"; } else { status.innerHTML = "CapsLocks disabled"; status.style.color = "blue"; } }, false);

<input type="text" id="text" /><br> <span id="status"></span>

This is a very old question. gilly3's answer is valid only if we have at hand an event object of type KeyboardEvent passed as a function argument. How to detect the current control key state if we have not event object available such as in this function?

function testModifierKey() { // have I some modifier key hold down at this running time? } 

I found the solution after a long search from https://gist.github.com/spikebrehm/3747378 of spikebrehm. his solution is tracing the modifier key state at any time using jQuery with a global variable.

The global variable window.modifierKey can be used in any circonstance without requiring event object.

function testModifierKey() { // have I have some modifier key hold down at this executing time? if(window.modifierKey) { console.log("Some modifier key among shift, ctrl, alt key is currently down."); // do something at this condition... for example, delete item without confirmation. } else { console.log("No modifier key is currently down."); // do something at other condition... for example, delete this item from shopping cart with confirmation. } } 

Here is his script to load in your HTML document:

// source: https://gist.github.com/spikebrehm/3747378 // modifierKey used to check if cmd+click, shift+click, etc. !function($, global){ var $doc = $(document); var keys; global.modifierKey = false; global.keys = keys = { 'UP': 38, 'DOWN': 40, 'LEFT': 37, 'RIGHT': 39, 'RETURN': 13, 'ESCAPE': 27, 'BACKSPACE': 8, 'SPACE': 32 }; // borrowed from Galleria.js var keyboard = { map: {}, bound: false, press: function(e) { var key = e.keyCode || e.which; if ( key in keyboard.map && typeof keyboard.map[key] === 'function' ) { keyboard.map[key].call(self, e); } }, attach: function(map){ var key, up; for(key in map) { if (map.hasOwnProperty(key)) { up = key.toUpperCase(); if (up in keyboard.keys) { keyboard.map[keyboard.keys[up]] = map[key]; } else { keyboard.map[up] = map[key]; } } } if (!keyboard.bound) { keyboard.bound = true; $doc.bind('keydown', keyboard.press); } }, detach: function() { keyboard.bound = false; keyboard.map = {}; $doc.unbind('keydown', keyboard.press); } }; $doc.keydown(function(e) { var key = e.keyCode || e.which; if (key === 16 || key === 91 || key === 18 || key === 17) { modifierKey = true; } else { modifierKey = false; } }); $doc.keyup(function(e) { modifierKey = false; }); }(jQuery, window);