Function isNumberAnd

Executes a type guard for the number type prior to testing a condition that requires an input of number type, returning true only if both the type check and condition pass.

Remarks

This is especially useful in pipelines where the TS type checker would not detect that a type guard had been applied using other alternatives.

Example

import * as G from "flurp/guard";
import * as L from "flurp/logic";

// isFinite is a JS built-in. While vanilla JS is tolerant,
// TS requires its parameter to be numeric.

const goodIsFinite = G.isNumberAnd(isFinite);
goodIsFinite(5);                // true
goodIsFinite(5/0);              // false
goodIsFinite("5");              // false

const badIsFinite = L.both(G.isNumber, isFinite);
badIsFinite("5");         // TS compiler will not recognize G.isNumber as a type guard.