isUndefined :: a β†’ Boolean
Evaluates whether the given value is undefined
import isUndefined from 'deep-waters/isUndefined';
isUndefined(undefined); // β†’ true
isUndefined(null); // β†’ false
isUndefined(false); // β†’ false
isUndefined, like any other type validator, is mostly used in composed validators:
import isString from 'deep-waters/isString';
import matchesPattern from 'deep-waters/matchesPattern';
const isEmail = compose(
isUndefined is built on top of ofClass validator and rely on Object.prototype.toString to check on the received value type in order to avoid typeof weird behaviours and encouraging a runtime strict type validation.
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