IE 11 automatically raises input validation when using " event : { 'input' } " and " hasFocus " binding

[ss13531]

I have an input which will be focused at the first time loading of page.
<input type='text' id='psName' data-bind=" textInput: name, css : { 'error' : isError }, enable: isAjaxLoading() === false, hasFocus: isFirstLoad, event : { 'input' : validate } "/>
"validate" will cause validate value of property "name", only check it is empty or not, then return "isError(true or false)".
"isAjaxLoading" is property which use to show/hide an "loading" image. The input will be enabled after loading page done ( = isAjaxLoading(false)).
When I test it with IE11, FF and Chrome (newest) I have 2 problems:

• Sometimes, the text input cannot be automatically focused (problem is on FF, Chrome, too) .
• If text input is automatically focused, the "validate" will automatically be called ( problem doesn't happen on FF, Chrome)

Summary, I want to resolve that how to set focus after the loading and render "enable" are done.
I used knockout 3.0.0.