Why does the form content disappear after selecting part of the content to print in javascript?

JavaScript When selecting part of the content to print, sometimes the form content disappears. This is because the browser only prints the visible part of the page by default when printing, and the form part is usually hidden and not within the visible area of ​​the page. , and therefore ignored by default. This article will show you how to solve this problem.

Problem Description

When we use JavaScript's window.print() method to print a page, we often find that part of the form is not printed, but only the visible part of the page is printed. . This is because the browser's default behavior is to print only the visible part of the page, and the form part is usually hidden and not within the visible area of ​​the page, so it is ignored by default.

Solution

In order to solve this problem, we need to use the @media media query in CSS. @media media query is a CSS technology that can provide different style sheets for web pages according to different media types to adapt to different terminal devices. We can use @media media queries to control how the form displays when printed.

The specific implementation steps are as follows:

1. Define a @media media query in the CSS style sheet:

@media print {
    /* 这里写规则 */
}

2. In the @media media query Write the display rules of the form in:

@media print {
    form {
        display: block;
        visibility: visible;
    }
}

In the above code, we use the two attributes display and visibility to control the display effect of the form when printing. Set the display property to block to display the form; set the visibility property to visible to make the form visible when printing.

3. Write the page style when printing in the @media media query:

@media print {
    form {
        display: block;
        visibility: visible;
    }
    
    /* 这里写其他规则，如文字大小、背景图等 */
}

In the above code, we can also add other rules, such as text size , background images, etc., to achieve better printing effects.

4. Call the window.print() method in JavaScript in the HTML page

Finally, call the window.print() method in the JavaScript in the HTML page , the print window should already contain the content of the form part.

<button>打印</button>

Summary

This article introduces the problem of form content disappearing when selecting part of the content for printing in JavaScript, and proposes a method to use @media media queries to solve this problem. By setting the rules in the @media media query, we can make the form display correctly when printing, thereby achieving better printing results.

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