isDouble
function isDouble(value: unknown): value is number;
A synonym of the Float family, offered under the name people reach for first. In JavaScript every number already is a double, so double names no runtime distinction of its own.
isX and nonX answer a question and never interrupt control flow; requireX and requireNonX hand the value back or throw. The scheme is explained in Validation conventions.
Parameters
Parameter | Type | Description |
|---|---|---|
|
| The value to check. |
Returns
boolean — true when the value is a number with a fractional part; otherwise false.
In TypeScript the guard narrows value to number inside the branch.
Examples
What passes and what does not
isDouble(1.5); // => true
isDouble(-0.1); // => true
isDouble(42); // => false
isDouble(1.0); // => false
isDouble(Infinity); // => false
isDouble("1.5"); // => false
See also
Source
23 September 2026
This documentation was generated with AI (Claude) from the library's source code.