1.map()方法 对数组中的每一个元素调用一种方法,不会改变原数组 exp: var arr = [ '10','20','30','40','50' ] var num1 = arr.map( ( el,index )=>{ el = el*2 // arr还是[ '10','20','30','40','50' ] } ) 2.forEach() 对数组中每一项元素调用一种方法,会改变原数组 exp: var arr = [ '10','20','30','40','50' ] var num1 = arr.forEach( (
