This feature is not Baseline because it does not work in some of the most widely-used browsers.
The blocking property of the HTMLScriptElement interface is a string indicating that certain operations should be blocked on the fetching of the script.
It reflects the blocking attribute of the <script> element.
A string. Must be a space-separated list of blocking tokens listed below indicating the operations that are to be blocked:
renderThe rendering of content on the screen is blocked.
Note: Only script elements in the document's <head> can possibly block rendering. Scripts are not render-blocking by default; if a script element does not include type="module", async, or defer, then it blocks parsing, not rendering. If such a script element is added dynamically via script, you must set blocking = "render" for it to block rendering.
<script id="el" type="text/javascript" async blocking="render"></script>
const el = document.getElementById("el");
console.log(el.blocking); // Output: "render"
| Specification |
|---|
| HTML> # dom-script-blocking> |
| Desktop | Mobile | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Chrome | Edge | Firefox | Opera | Safari | Chrome Android | Firefox for Android | Opera Android | Safari on IOS | Samsung Internet | WebView Android | WebView on iOS | |
blocking |
105 | 105 | No | 91 | 18.2 | 105 | No | 72 | 18.2 | 20.0 | 105 | 18.2 |
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https://developer.mozilla.org/en-US/docs/Web/API/HTMLScriptElement/blocking