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Showing content from https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Errors/Identifier_after_number below:

SyntaxError: identifier starts immediately after numeric literal - JavaScript

SyntaxError: identifier starts immediately after numeric literal

The JavaScript exception "identifier starts immediately after numeric literal" occurs when an identifier started with a digit. Identifiers can only start with a letter, underscore (_), or dollar sign ($).

Message

SyntaxError: Invalid or unexpected token (V8-based)
SyntaxError: identifier starts immediately after numeric literal (Firefox)
SyntaxError: No identifiers allowed directly after numeric literal (Safari)

Error type What went wrong?

The names of variables, called identifiers, conform to certain rules, which your code must adhere to!

A JavaScript identifier must start with a letter, underscore (_), or dollar sign ($). They can't start with a digit! Only subsequent characters can be digits (0-9).

Examples Variable names starting with numeric literals

Variable names can't start with numbers in JavaScript. The following fails:

const 1life = "foo";
// SyntaxError: identifier starts immediately after numeric literal

const foo = 1life;
// SyntaxError: identifier starts immediately after numeric literal

You will need to rename your variable to avoid the leading number.

const life1 = "foo";
const foo = life1;

In JavaScript, there is a syntactic peculiarity when calling properties or methods on numbers. If you want to call a method on an integer, you cannot immediately use a dot after the number because the dot is interpreted as the start of a decimal fraction, causing the parser to see the method's name as an identifier immediately after a number literal. To avoid this, you need to either wrap the number in parentheses or use a double dot, where the first dot is a decimal point for the number literal and the second dot is the property accessor.

alert(typeof 1.toString())
// SyntaxError: identifier starts immediately after numeric literal

Correct ways to call methods on numbers:

// Wrap the number in parentheses
alert(typeof (1).toString());

// Add an extra dot for the number literal
alert(typeof 2..toString());

// Use square brackets
alert(typeof 3["toString"]());