map:
array2 = array.map( v => v + 1 ) 可以写成 array2 = array.reduce((result, v) => { result.push(v + 1) return result }, [])
filter
array2 = array.filter(v => v % 2 === 0) 可以写成 array2 = array.reduce((result, v) => { if(v % 2 === 0) { result.push(v) } return result }, [])