手写typeof

 function myTypeof(x) {
            let a = Object.prototype.toString.call(x).slice(8, -1).toLowerCase()
            let t = [
                'number',
                'bigint',
                'string',
                'symbol',
                'function',
                'boolean',
                'undefined'
            ]
            if (t.indexOf(a) != -1)
                return a
            else
                return 'object'
        }