这样做。

如果你的元素是这样的…

<input type="text" id="mytext"/>

你的剧本应该是

<script>
function setFocusToTextBox(){
    document.getElementById("mytext").focus();
}
</script>

这样做。

如果你的元素是这样的…

<input type="text" id="mytext"/>

你的剧本应该是

<script>
function setFocusToTextBox(){
    document.getElementById("mytext").focus();
}
</script>

试试这个:

$('.modal').on('shown.bs.modal', function () {
        setTimeout(function() {
                $("input#yourFieldId").addClass('modal-primary-focus').focus();
            },
            500);
    });

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();
};

这个例子对我很有用

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