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version: "1.0.2" name: mongez-supportive-is-overview description: | High-level introduction to @mongez/supportive-is — a tree-shakable library of ~60 type and shape predicates with server-safe imports.

@mongez/supportive-is — Overview

A small library of type and shape predicates — isString, isEmpty, isUrl, isPromise, isMobile.*, and friends. Each one is a named export, so bundlers drop the ones you don't use. Pure predicates run anywhere; DOM-touching predicates read globals lazily so server-side imports stay safe.

Highlighted features

<div class="mongez-highlight" data-accent="ice"> <svg class="mongez-highlight-icon" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" aria-hidden="true"><polyline points="9 11 12 14 22 4"/><path d="M21 12v7a2 2 0 0 1-2 2H5a2 2 0 0 1-2-2V5a2 2 0 0 1 2-2h11"/></svg> <h3>~60 named predicates</h3> <p>One named export per predicate — <code>isString</code>, <code>isEmail</code>, <code>isUrl</code>, <code>isPromise</code>, <code>isPlainObject</code>, dozens more.</p> </div>

<div class="mongez-highlight" data-accent="ice"> <svg class="mongez-highlight-icon" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" aria-hidden="true"><path d="M17 8C8 10 5.9 16.17 3.82 21.34l1.89.66.95-2.3c.48.17.98.3 1.34.3C19 20 22 3 22 3c-1 2-8 2.25-13 3.25S2 11.5 2 13.5s1.75 3.75 1.75 3.75"/></svg> <h3>Tree-shake to ~80 bytes</h3> <p><code>sideEffects: false</code> + per-predicate exports. Pull <code>isEmail</code> alone and ship ~80 bytes, not the whole 3KB bag.</p> </div>

<div class="mongez-highlight" data-accent="fire"> <svg class="mongez-highlight-icon" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" aria-hidden="true"><path d="M12 22s8-4 8-10V5l-8-3-8 3v7c0 6 8 10 8 10z"/></svg> <h3>Server-safe imports</h3> <p>DOM/browser predicates read <code>navigator</code> / <code>window</code> / <code>document</code> lazily. Safe to import on the server; <code>isFormElement</code> returns <code>false</code> there instead of throwing.</p> </div>

<div class="mongez-highlight" data-accent="bolt"> <svg class="mongez-highlight-icon" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" aria-hidden="true"><circle cx="12" cy="12" r="10"/><line x1="12" y1="8" x2="12" y2="12"/><line x1="12" y1="16" x2="12.01" y2="16"/></svg> <h3>"Smart" emptiness</h3> <p><code>isEmpty</code> collapses <code>null</code> / <code>undefined</code> / <code>""</code> / <code>[]</code> / <code>{}</code> / Maps / Sets into one check. <code>0</code> and <code>false</code> are deliberately NOT empty.</p> </div>

</div>

Install

npm install @mongez/supportive-is
# or: yarn add @mongez/supportive-is
# or: pnpm add @mongez/supportive-is

Quick peek

import { isEmail, isEmpty, isPlainObject, isUrl } from "@mongez/supportive-is";
isEmail("user@example.com");   // true
isEmpty({});                   // true
isEmpty(0);                    // false  — zero is a real value
isPlainObject(new Date());     // false  — Date is an instance, not a literal
isUrl("https://example.com");  // true

Tree-shakable predicates — import only what you use.

Mental model

Concept	What it means
Pure predicates	Single-argument functions on `unknown`: take a value, return a boolean. Twelve are real TypeScript type predicates (`value is T`). No side effects, no allocation.
`Is` namespace	A bag of references to the same functions, kept for v1 compatibility. Doesn't tree-shake — prefer named imports.
Environment probes	Touch `navigator` / `window` / `document` at call time. Server-safe to import, server-unsafe to call.
"Smart" emptiness	`isEmpty` collapses null / undefined / "" / [] / {} / `new Map()` / `new Set()` into one check, with `0` and `false` deliberately not empty.

Scope boundaries

Concern	Lives in	Why
General object/string/array helpers	`@mongez/reinforcements`	Different package, different scope
Schema validation (`z.string().email()`)	`zod`, `valibot`	Predicates are guards, not validators
HTML sanitization	`DOMPurify`	Regex-based stripping is a footgun

Where to go next

[Primitives](../primitives/) — isString, isNumber, isBoolean, isFunction, etc.
[Collections](../collections/) — isArray, isPlainObject, isMap, isSet, isEmpty
[Formats](../formats/) — isEmail, isUrl, isJson, isIp
[Environment](../environment/) — isBrowser, isMobile, isMac, vendor probes
[Misc](../misc/) — edge-case predicates
[Recipes](../recipes/) — composition patterns

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