vizoy

``` js function getType(v) { return v === undefined ? 'undefined' : v === null ? 'null' : v.constructor.name } ```

``` js ;[...Array(10000).keys()].filter((v) => { return v === Number( (String(v).match(/(^\d)(\d)?\2*\1$/) || [])[0] ) }) 精简一下 ;[...Array(10000).keys()].filter(v => { return (String(v).match(/(^\d)(\d)?\2*\1$/) || [])[0] }) 再精简一下 ;[...Array(1e4).keys()].filter(v => (v+'').match(/(^\d)(\d)?\2*\1$/)) ```