这是一个正常的文本框活动。

单击“1 -设置焦点”

点击2/3(双击)-选择文本

您可以在页面第一次加载时将焦点设置在文本框上，以减少“选择”为单个双击事件。

在输入字段中使用“占位符”而不是“值”。

以下是Shoban回答的可重复使用版本:

<input type="text" id="userid" name="userid"
 value="Please enter the user ID" onfocus="Clear(this);"
/>

function Clear(elem)
{
elem.value='';
}

这样就可以为多个元素重用clear脚本。

你所问问题的确切解决方案是:

<input type="text" id="userid" name="userid" value="Please enter the user ID" onClick="this.setSelectionRange(0, this.value.length)"/>

但是我猜想，您试图在输入中显示“请输入用户ID”作为占位符或提示。 因此，您可以使用以下更有效的解决方案:

<input type="text" id="userid" name="userid" placeholder="Please enter the user ID" />

之前发布的解决方案有两个怪癖:

在Chrome中，通过.select()选择不粘-添加一个轻微的超时解决了这个问题。 不可能在聚焦后将光标放置在所需的点上。

这里有一个完整的解决方案，选择焦点上的所有文本，但允许在焦点后选择特定的游标点。

$(function () {
    var focusedElement;
    $(document).on('focus', 'input', function () {
        if (focusedElement == this) return; //already focused, return so user can now place cursor at specific point in input.
        focusedElement = this;
        setTimeout(function () { focusedElement.select(); }, 100); //select all text in any field on focus for easy re-entry. Delay sightly to allow focus to "stick" before selecting.
    });
});

If you are just trying to have placeholder text that gets replaced when a user selects the element then it is obviously best practice to use placeholder attribute nowadays. However, if you want to select all of the current value when a field gains focus then a combination of @Cory House and @Toastrackenigma answers seems to be most canonical. Use focus and focusout events, with handlers that set/release the current focus element, and select all when focused. An angular2/typescript example is as follows (but would be trivial to convert to vanilla js):

模板:

<input type="text" (focus)="focus()" (focusout)="focusout()" ... >

组件:

private focused = false;

public focusout = (): void => {
    this.focused = false;
};

public focus = (): void => {
    if(this.focused) return;
    this.focused = true;

    // Timeout for cross browser compatibility (Chrome)
    setTimeout(() => { document.execCommand('selectall', null, false); });
};