Friday, October 10, 2025
HomeLanguagesJavascriptJavaScript SyntaxError – “x” is not a legal ECMA-262 octal constant

JavaScript SyntaxError – “x” is not a legal ECMA-262 octal constant

This JavaScript warning 08 (or 09) is not a legal ECMA-262 octal constant that occurs if the literals 08 or 09 are used as a number. This occurs because these literals cannot be treated as an octal number.

Message:

Warning: SyntaxError: 08 is not a legal ECMA-262 octal constant.
Warning: SyntaxError: 09 is not a legal ECMA-262 octal constant.

Error Type:

Warning. JavaScript execution won't be halted.

Cause of Error: This happens when any of the digits after the leading 0 is equal to or greater than 8. This number cannot be treated as an octal number and therefore JavaScript gives a warning about it.

Example 1: In this example, the literal ’08’ gives a warning because it can not be interpreted as an octal number.

Javascript




"use strict";
// Error here
08;


Output:

Warning: SyntaxError: 08 is not a legal ECMA-262 octal constant.

Example 2: In this example, the literal ’09’ gives a warning because it can not be interpreted as an octal number.

Javascript




"use strict";
// Error here
09;


Output:

Warning: SyntaxError: 09 is not a legal ECMA-262 octal constant.
Whether you’re preparing for your first job interview or aiming to upskill in this ever-evolving tech landscape, neveropen Courses are your key to success. We provide top-quality content at affordable prices, all geared towards accelerating your growth in a time-bound manner. Join the millions we’ve already empowered, and we’re here to do the same for you. Don’t miss out – check it out now!
Dominic
Dominichttp://wardslaus.com
infosec,malicious & dos attacks generator, boot rom exploit philanthropist , wild hacker , game developer,
RELATED ARTICLES

Most Popular

Dominic
32349 POSTS0 COMMENTS
Milvus
87 POSTS0 COMMENTS
Nango Kala
6715 POSTS0 COMMENTS
Nicole Veronica
11878 POSTS0 COMMENTS
Nokonwaba Nkukhwana
11941 POSTS0 COMMENTS
Shaida Kate Naidoo
6837 POSTS0 COMMENTS
Ted Musemwa
7097 POSTS0 COMMENTS
Thapelo Manthata
6792 POSTS0 COMMENTS
Umr Jansen
6791 POSTS0 COMMENTS