1 // Copyright (c) 2013 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 function focus(element) { 6 // Focus the target element in order to send keys to it. 7 // First, the currently active element is blurred, if it is different from 8 // the target element. We do not want to blur an element unnecessarily, 9 // because this may cause us to lose the current cursor position in the 10 // element. 11 // Secondly, we focus the target element. 12 // Thirdly, if the target element is newly focused and is a text input, we 13 // set the cursor position at the end. 14 // Fourthly, we check if the new active element is the target element. If not, 15 // we throw an error. 16 // Additional notes: 17 // - |document.activeElement| is the currently focused element, or body if 18 // no element is focused 19 // - Even if |document.hasFocus()| returns true and the active element is 20 // the body, sometimes we still need to focus the body element for send 21 // keys to work. Not sure why 22 // - You cannot focus a descendant of a content editable node 23 // - V8 throws a TypeError when calling setSelectionRange for a non-text 24 // input, which still have setSelectionRange defined. For chrome 29+, V8 25 // throws a DOMException with code InvalidStateError. 26 var doc = element.ownerDocument || element; 27 var prevActiveElement = doc.activeElement; 28 if (element != prevActiveElement && prevActiveElement) 29 prevActiveElement.blur(); 30 element.focus(); 31 if (element != prevActiveElement && element.value && 32 element.value.length && element.setSelectionRange) { 33 try { 34 element.setSelectionRange(element.value.length, element.value.length); 35 } catch (error) { 36 if (!(error instanceof TypeError) && !(error instanceof DOMException && 37 error.code == DOMException.INVALID_STATE_ERR)) 38 throw error; 39 } 40 } 41 if (element != doc.activeElement) 42 throw new Error('cannot focus element'); 43 } 44
