使用 javascript 或 jQuery 生成 CSS 媒体查询

Question

Is it possible to create full media query rules on the fly using Javascript or jQuery?

I've used numerous media queries to target generalised viewports and specific devices/screens using inline CSS, imports and linked files:

@media screen and (min-width:400px) { ... }
@import url(foo.css) (min-width:400px);
<link rel="stylesheet" type="text/css" media="screen and (min-width: 400px)" href="foo.css" />

I can add/remove classes using jQuery:

$("foobar").click(function(){
  $("h1,h2,h3").addClass("blue");
  $("div").addClass("important");
  $('#snafu').removeClass('highlight');
});

I've also look at document.stylesheets and the seemingly archaic and browser-specific:

  document.styleSheets[0].insertRule("p{font-size: 20px;}", 0)

But I can't find any reference to programatically generating:

  @media screen and (min-width:400px)

from javascript directly or in any form.

Answer 1

You can just update an existing <style> element (or create one) textContent to contain the rule, which will make it effective in the given context.

document.querySelector('style').textContent +=
    "@media screen and (min-width:400px) { div { color: red; }}"

http://jsfiddle.net/vfLS3/

Answer 2

I use this way. This allows to update multiply styles in document

in HTML:

<style class="background_image_styles">
</style>

in JS

$(".background_image_styles").text("@media (min-width: 1200px) {.user_background_image{background-image: url('https://placehold.it/1200x300');}}");

Answer 3

For general purpose use, you can append a style sheet to document.head . Then you can put any mods in there you want -- including media queries. Since it's the final style sheet in document.head , it overrides any prior CSS rules.

Vanilla JavaScript:

    let style = document.getElementById('custom-styles');
    if (!style) {
      style = document.createElement('style');
      style.id = "custom-styles";
      document.head.appendChild(style);
    }
    style.innerHTML =
      "@media screen and (min-width:400px) {...}";

Answer 4

I prefer this variant - appending to the end of the head section:

$('<style/>', {
    text: '@media print { @page { margin: 10 20 20 10; } body { margin: 0.5cm; }}',
    appendTo: win.document.head
})