javascript类型判断

代码实现

index.js

const myTypeof = function (value) {
    let type = typeof value
    if (value === null) { // null比较特殊，typeof null = 'object'
        return 'null'
    } else if (type === 'object') { // array、object、Date、RegExp 的typeof都为'object'
        // Object.prototype.toString.call([])返回格式[object Array]
        return Object.prototype.toString.call(value).replace(/^\[object\s(\w+)\]$/, '$1')
    } else {
        return type
    }
}

测试例子

index.test.js

let myTyepeof = require('./index.js')

test('Number:', () => {
    expect(myTyepeof(123)).toBe('number')
})

test('String:', () => {
    expect(myTyepeof('123')).toBe('string')
})

test('Boolean:', () => {
    expect(myTyepeof(true)).toBe('boolean')
})

test('Null:', () => {
    expect(myTyepeof(null)).toBe('null')
})

test('Undefined:', () => {
    expect(myTyepeof(undefined)).toBe('undefined')
})

test('Arrary:', () => {
    expect(myTyepeof([1, 2, 3])).toBe('Array')
})

test('Object:', () => {
    expect(myTyepeof({a:1})).toBe('Object')
})

test('Date:', () => {
    expect(myTyepeof(new Date())).toBe('Date')
})

test('RegExp:', () => {
    expect(myTyepeof(new RegExp())).toBe('RegExp')
})

test('Symbol', () => {
    expect(myTyepeof(Symbol())).toBe('symbol')
})

测试结果