- push改变原数组;cancat不改变原数组，返回一个新数组
let arr1 = [1,2,3]
arr1.push(4)
console.log(arr);//[1,2,3,4]
let arr2 = [1,2,3]
let arr3 = arr2.concat(4)
console.log(arr2)//[1,2,3]
console.log(arr3)//[1,2,3,4]
2.当参数不为数组时达到的效果一样
//参数不为数组
let arr4 = [1,2,3]
arr4.push(4,5)
console.log(arr4)//[1,2,3,4,5]
let arr5 = [1,2,3]
let arr6 = arr5.concat(4,5)
console.log(arr6)[1,2,3,4,5]
//参数包含数组
arr4.push(6,[7,8])
//push会直接添加数组作为一项
console.log(arr5)//[1,2,3,4,5,6,[7,8]]
//cancat 会展开数组，添加数组的值
arr6 = arr6.concat(6,[7,8])
console.log(arr6)//[1,2,3,4,5,6,7,8]
