String.prototype.sub()
Deprecated: This feature is no longer recommended. Though some browsers might still support it, it may have already been removed from the relevant web standards, may be in the process of being dropped, or may only be kept for compatibility purposes. Avoid using it, and update existing code if possible; see thecompatibility table at the bottom of this page to guide your decision. Be aware that this feature may cease to work at any time.
Thesub() method ofString values creates a string that embeds this string in a<sub> element (<sub>str</sub>), which causes this string to be displayed as subscript.
Note:AllHTML wrapper methods are deprecated and only standardized for compatibility purposes. UseDOM APIs such asdocument.createElement() instead.
Syntax
sub()Parameters
None.
Return value
A string beginning with a<sub> start tag, then the textstr, and then a</sub> end tag.
Examples
Using sub()
The code below creates an HTML string and then replaces the document's body with it:
const contentString = "Hello, world";document.body.innerHTML = contentString.sub();This will create the following HTML:
<sub>Hello, world</sub>Instead of usingsub() and creating HTML text directly, you should use DOM APIs such asdocument.createElement(). For example:
const contentString = "Hello, world";const elem = document.createElement("sub");elem.innerText = contentString;document.body.appendChild(elem);Specifications
| Specification |
|---|
| ECMAScript® 2026 Language Specification # sec-string.prototype.sub |