How to set the page paper size in javascript

JavaScript can help us dynamically set a series of properties of the web page, including paper size. This feature can be used to build an adaptive printing page that meets the various needs of the user's printing needs. In this article, we'll show you how to use JavaScript to set the page paper size and use stylesheets to optimize pages for printing.

1. Set the paper size of the webpage

There are two main ways to set the paper size of the webpage: one is to set the paper size through CSS style sheet, and the other is to dynamically set the paper size through JavaScript. .

1. CSS style sheet to set paper size

You can set the web page paper size through CSS style sheet. In CSS, we can use the @page rule to control the properties of the printed page. Below is an example that shows how to use a CSS stylesheet to set the paper size.

@page {
  size: A4 landscape;
}

In the above code, we set the paper size to A4 (210mm × 297mm) landscape. Similarly, we can also set it to other sizes, such as A5 portrait, letter landscape, etc. This way of setting up CSS is very simple, but there is a problem: not all browsers support the @page rule. Therefore, we need to consider browser compatibility issues.

2. JavaScript to dynamically set the paper size

If we need to have better control over the paper size, we can use JavaScript to dynamically set the paper size. JavaScript provides a print method for printing the current window or the specified document. In the print method, we can use the pageWidth and pageHeight properties to control the paper size. Below is a simple example showing how to dynamically set the paper size using JavaScript.

function printPage() {
  var printPageWidth = 210;
  var printPageHeight = 297;

  // 创建一个新的打印窗口
  var printWindow = window.open('', '', 'width=794, height=1123');

  // 通过标准化处理来计算纸张大小
  printPageWidth = Math.floor(printPageWidth * 3.779527559) + 'px';
  printPageHeight = Math.floor(printPageHeight * 3.779527559) + 'px';

  // 设置纸张大小
  printWindow.document.body.style.width = printPageWidth;
  printWindow.document.body.style.height = printPageHeight;

  // 写入要打印的内容
  printWindow.document.write('<h1>Hello World!</h1>');

  // 关闭写入流，开始打印
  printWindow.document.close();
  printWindow.focus();
  printWindow.print();
  printWindow.close();
}

In the above code, we first define the width and height of the paper. We then convert these two values ​​to pixel units according to the normalization process and set them to the body element of the print window. Next, we write some content to be printed in the newly opened window. Finally, we call the print() method to trigger the printing function and close the window after printing is completed.

It should be noted that this method requires manual triggering of printing, and it cannot avoid browser compatibility issues. Therefore, we need to consider careful testing and debugging before use.

2. Use style sheets to optimize printing pages

In the process of realizing adaptive printing pages, style sheets play a vital role. Here are some tips for using style sheets to optimize printed pages.

1. Manually set headers and footers

Using style sheets to set custom headers and footers can make our printed pages more professional. Below is a simple example that shows how to set a header and footer using CSS stylesheets.

@media print {
  @page {
    size: A4 portrait;
    margin: 1cm;
    @top-center { content: "MY HEADER"; }
    @bottom-center { content: "MY FOOTER"; }
  }
}

In the above code, we use the @content attribute to define custom header and footer. In this way, we can add our own logo, address, contact information, etc. to the printed page.

2. Hide unnecessary elements

In the printed page, some elements do not need to be printed, such as menu bars, banners, advertisements, etc. Therefore, we need to use a stylesheet to hide these elements. Below is a simple example showing how to use a CSS stylesheet to hide an element.

@media print {
  #menu, #banner, .ad {
    display: none !important;
  }
}

In the above code, we use the display attribute to hide elements such as menu bar, banners and ads. It should be noted here that since we need to ensure that these elements will not be printed, we use the @media print pseudo-class and the !important keyword to ensure the priority of the style rules Highest.

3. Conclusion

In this article, we introduced how to use JavaScript to dynamically set the web page paper size and use CSS style sheets to optimize the printed page. It should be noted that sufficient testing and debugging are required when using these techniques to ensure compatibility across different browsers and devices. If we can use these techniques correctly, we can build an excellent adaptive printing page and bring a better printing experience to users.

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