js数据类型以及其判断方法实例

let a = 1,
 b = '2',
 c = true,
 d = undefined,
 e = null,
 f = Symbol('f'),
 g = function () {},
 h = [],
 i = new Date()
console.log(typeof a)
console.log(typeof b)
console.log(typeof c)
console.log(typeof d)
console.log(typeof e)
console.log(typeof f)
console.log(typeof g)
console.log(typeof h)
console.log(typeof i)

function checkNull(num) {
 return num === null
}

function checkObject(obj) {
 return Object.prototype.toString.call(obj)
}
console.log(checkObject(g))
console.log(checkObject(h))
console.log(checkObject(i))

console.log(g.constructor === Function)
console.log(h.constructor === Array)
console.log(i.constructor === Date)