这个例子对我很有用

$(document).ready(function () {
document.getElementById('TextBox').focus();
}

如前所述，文档。表单也有用。

function setFocusToTextBox( _element ) {
  document.forms[ 'myFormName' ].elements[ _element ].focus();
}

setFocusToTextBox( 0 );
// sets focus on first element of the form

Thought of sharing some edge cases for this subject. If your content is reloading (example dynamic DOM loading results from API and setting focus on first item of results) adding attribute autofocus will not be your solution, it works only on first load, second DOM change will not work but works fine in static DOM or single page load. If you have Dynamic component loading data simple .focus() will fail due to triggering focus on element not created yet by the time focus() is or blur not complete yet by DOM. For this case expected is to add delay time (setTimeout function) to give a time for focus to apply to new created or recreated element in DOM. My case was to load data from API and get focus on first result. Adding var el = document.getElementById(focusId); el.focus(); solved the issue so DOM completes blur without adding delay.

对于简单的Javascript，试试下面的代码:

window.onload = function() {
  document.getElementById("TextBoxName").focus();
};

窗口。Onload是最初放置焦点 Onblur是将焦点放在文本区域外，或避开文本区域 模糊

    <textarea id="focus"></textarea>
    <script>
     var mytexarea=document.getElementById("focus");
    window.onload=function()
    {
   
    mytexarea.focus();
    
    }
    

    </script>

不管怎样，你可以在HTML5兼容浏览器上使用自动聚焦属性。甚至可以在IE版本10上使用。

<input name="myinput" value="whatever" autofocus />