JS 判断值是否为 undefinedJS 和是否为数组

001 JS 判断值是否为 undefined

    export function isDef(v) { 
        return v !== undefined && v !== null
    }

002 JS 判断是否为数组

    const toString = Object.prototype.toString
    
    const ARRAY_TYPE = '[object Array]'
    export function isArray(v) {
        return toString.call(v) === ARRAY_TYPE
    }

【拓展阅读】深入理解Object.prototype.toString.call()
https://www.jianshu.com/p/e4237ebb1cf0

export function noop(v) {
  return v
}

const BOOLEAN = 'boolean'
export function isBoolean(v) {
  return typeof v === BOOLEAN
}

const STRING = 'string'
export function isString(v) {
  return typeof v === STRING
}

const FUNCTION = 'function'
export function isFunction(v) {
  return typeof v === FUNCTION
}

export function runAsFn(v) {
  return isFunction(v) ? v() : v
}

const NUMBER = 'number'
export function isNumber(v) {
  return !isNaN(v) && typeof v === NUMBER
}

const OBJECT = 'object'
export function isObject(v) {
  return typeof v === OBJECT && v !== NULL
}

export function isWindow(v) {
  return v !== NULL && v === v.window
}