//(1)在数组末尾追加一个元素,返回追追加元素后数组的长度 var array=["String","Number","Undefined","Null","Boolean"]; var return_value=array.push(123); console.log(return_value); console.log(array); //(2)在数组开头追加一个元素,返回追加元素后数组的长度 var array=["String","Number","Undefined","Null","Boolean"]; var return_value=array.unshift(123); console.log(return_value); console.log(array);