HTMLScriptElement

Inherits properties from its parent, HTMLElement.

HTMLScriptElement.async

A boolean value that controls how the script should be executed. For classic scripts, if the async property is set to true, the external script will be fetched in parallel to parsing and evaluated as soon as it is available. For module scripts, if the async property is set to true, the script and all their dependencies will be fetched in parallel to parsing and evaluated as soon as they are available.

HTMLScriptElement.charset Deprecated

A string representing the character encoding of an external script. It reflects the charset attribute.

HTMLScriptElement.crossOrigin

A string reflecting the CORS setting for the script element. For classic scripts from other origins, this controls if error information will be exposed.

HTMLScriptElement.defer

A boolean value that controls how the script should be executed. For classic scripts, if the defer property is set to true, the external script will be executed after the document has been parsed, but before firing DOMContentLoaded event. For module scripts, the defer property has no effect.

HTMLScriptElement.event Deprecated

A string; an obsolete way of registering event handlers on elements in an HTML document.

HTMLScriptElement.fetchPriority

An optional string representing a hint given to the browser on how it should prioritize fetching of an external script relative to other external scripts. If this value is provided, it must be one of the possible permitted values: high to fetch at a high priority, low to fetch at a low priority, or auto to indicate no preference (which is the default). It reflects the fetchpriority attribute of the <script> element.

HTMLScriptElement.integrity

A string that contains inline metadata that a browser can use to verify that a fetched resource has been delivered without unexpected manipulation. It reflects the integrity attribute of the <script> element.

HTMLScriptElement.noModule

A boolean value that if true, stops the script's execution in browsers that support ES modules — used to run fallback scripts in older browsers that do not support JavaScript modules.

HTMLScriptElement.referrerPolicy

A string that reflects the referrerPolicy HTML attribute indicating which referrer to use when fetching the script, and fetches done by that script.

HTMLScriptElement.src

A string representing the URL of an external script; this can be used as an alternative to embedding a script directly within a document. It reflects the src attribute of the <script> element.

HTMLScriptElement.text

A string that joins and returns the contents of all Text nodes inside the <script> element (ignoring other nodes like comments) in tree order. On setting, it acts the same way as the Node.textContent property.

Note: When inserted using the Document.write() method, <script> elements execute (typically synchronously), but when inserted using Element.innerHTML or Element.outerHTML, they do not execute at all.

HTMLScriptElement.type

A string representing the type of the script. It reflects the type attribute of the <script> element.

HTMLScriptElement.supports()

Returns true if the browser supports scripts of the specified type and false otherwise. This method provides a simple and unified method for script-related feature detection.

No specific methods; inherits methods from its parent, HTMLElement.

No specific events; inherits events from its parent, HTMLElement.

Let's create a function that imports new scripts within a document creating a <script> node immediately before the <script> that hosts the following code (through document.currentScript). These scripts will be asynchronously executed. For more details, see the defer and async properties.

function loadError(oError) {
  throw new URIError(`The script ${oError.target.src} didn't load correctly.`);
}

function prefixScript(url, onloadFunction) {
  const newScript = document.createElement("script");
  newScript.onerror = loadError;
  if (onloadFunction) {
    newScript.onload = onloadFunction;
  }
  document.currentScript.parentNode.insertBefore(
    newScript,
    document.currentScript,
  );
  newScript.src = url;
}

This next function, instead of prepending the new scripts immediately before the document.currentScript element, appends them as children of the <head> tag.

function loadError(oError) {
  throw new URIError(`The script ${oError.target.src} didn't load correctly.`);
}

function affixScriptToHead(url, onloadFunction) {
  const newScript = document.createElement("script");
  newScript.onerror = loadError;
  if (onloadFunction) {
    newScript.onload = onloadFunction;
  }
  document.head.appendChild(newScript);
  newScript.src = url;
}

Sample usage:

affixScriptToHead("myScript1.js");
affixScriptToHead("myScript2.js", () => {
  alert('The script "myScript2.js" has been correctly loaded.');
});

HTMLScriptElement.supports() provides a unified mechanism for checking whether a browser supports particular types of scripts.

The example below shows how to check for module support, using the existence of the noModule attribute as a fallback.

function checkModuleSupport() {
  if ("supports" in HTMLScriptElement) {
    return HTMLScriptElement.supports("module");
  }
  return "noModule" in document.createElement("script");
}

Classic scripts are assumed to be supported on all browsers.

• HTML <script> element
• HTML <noscript> element
• document.currentScript
• Web Workers (code snippets similar to scripts but executed in another global context)