whether-is

中文说明请见下方

A comprehensive, extensible, and type-friendly type and value checking utility for JavaScript/TypeScript.

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Features

• Rich type and value checking: supports primitives, objects, arrays, classes, special values, and more
• Handles edge cases (cross-realm, etc.)
• TypeScript friendly, with type guards
• Extensible and easy to use

Installation

npm install whether-is

Usage

import { whether } from 'whether-is';

whether.isString('abc'); // true
whether.isNumber(123); // true
whether.isArray([1, 2, 3]); // true
whether.isNullish(undefined); // true
whether.likeDate(new Date()); // true
whether.likePromise(Promise.resolve()); // true

// specially
whether.isNaN(NaN); // true
whether.isNaN(232); // false
whether.isNaN('abc'); // null <- not false!

API Highlights

• is, equal(deep)
• isString, isNumber, isBoolean, isNull, isUndefined, isSymbol, isBigInt
• isObject, likeObject, isArray, isFunction, isClass, isArrowFunction
• isEmpty, isEmptyObject, isEmptyArray, isNaN, isInteger, isSafeInteger, isSafeNumber, isFinite, isPrimitive, isField, isPropertyKey
• likeError, likeDate, likePromise, likeSet, likeMap, likeWeakSet, likeWeakMap, likeRegExp
• All orXXX methods support optional/undefined values

Notable Functions

• isNaN:

  • Returns true only for the real NaN value, false for numbers, and null for non-number types (e.g. isNaN('abc') === null). This avoids the pitfalls of the global isNaN and is more type-safe.

• likeXXX series (e.g. likeDate, likeSet, likePromise):

  • These check if an object is structurally similar to a built-in type, not just by instanceof, but by comparing all prototype property types. Useful for cross-realm/iframe and polyfilled objects.

• isArrowFunction:

  • Detects arrow functions, even if not a standard function constructor. Handles most edge cases except proxied functions.
  • For precise results, see https://github.com/baendlorel/get-function-features

• isClass:

  • Checks if a function is a class constructor, not just a plain function. Uses proxy and string analysis for accuracy.
  • For precise results, see https://github.com/baendlorel/get-function-features

• isPromiseLike:

  • Checks if an object is a thenable (Promise A+ spec), not just a native Promise instance.

• isEmpty, isEmptyObject, isEmptyArray:

  • Fine-grained checks for various empty states, including objects with no keys, arrays of length 0, and falsy values.

Edge Case Handling

• Cross-realm (iframe) objects
• Proxy objects
• Custom class inheritance
• Array-like objects

License

MIT

中文说明

一个全面、可扩展、类型友好的 JavaScript/TypeScript 类型和值判定工具库。

特性

• 丰富的类型和值判定：支持原始类型、对象、数组、类、特殊值等
• 处理各种边界情况（跨 iframe 等）
• TypeScript 友好，类型守卫
• 可扩展、易用

安装

npm install whether-is

用法示例

import { whether } from 'whether-is';

whether.isString('abc'); // true
whether.isNumber(123); // true
whether.isArray([1, 2, 3]); // true
whether.isNullish(undefined); // true
whether.likeDate(new Date()); // true
whether.likePromise(Promise.resolve()); // true

// 特别情况
whether.isNaN(NaN); // true
whether.isNaN(232); // false
whether.isNaN('abc'); // null <- 不是 false!

主要 API

• is, equal(deep)
• isString, isNumber, isBoolean, isNull, isUndefined, isSymbol, isBigInt
• isObject, likeObject, isArray, isFunction, isClass, isArrowFunction
• isEmpty, isEmptyObject, isEmptyArray, isNaN, isInteger, isSafeInteger, isSafeNumber, isFinite, isPrimitive, isField, isPropertyKey
• likeError, likeDate, likePromise, likeSet, likeMap, likeWeakSet, likeWeakMap, likeRegExp
• 所有 orXXX 方法支持可选/undefined 判定

特色判定函数

• isNaN：

  • 只对真正的 NaN 返回 true，对数字返回 false，对非数字类型（如字符串）返回 null，避免了全局 isNaN 的误判，更加类型安全。

• likeXXX 系列（如 likeDate, likeSet, likePromise）：

  • 不仅仅用 instanceof，还会比较原型链上所有属性的 typeof，能识别跨 iframe、polyfill 等场景的“类实例”。

• isArrowFunction：

  • 检测箭头函数，能区分普通函数和箭头函数（除 proxy 情况外）。
  • 更准确的判定参见：https://github.com/baendlorel/get-function-features

• isClass：

  • 判断一个函数是否为 class 构造器，而非普通函数。结合 proxy 和字符串分析，准确率高。
  • 更准确的判定参见：https://github.com/baendlorel/get-function-features

• isPromiseLike：

  • 判断对象是否为 Promise-like（thenable，符合 Promise A+ 规范），不仅限于原生 Promise。

• isEmpty、isEmptyObject、isEmptyArray：

  • 细致区分各种“空”状态，包括无键对象、空数组、falsy 值等。

边界情况支持

• 跨 iframe（跨全局环境）对象
• Proxy 对象
• 自定义类继承
• 类数组对象

许可证

MIT