1、splice函数

let a = [1,2]
a.splice(0,a.length)
console.log(a);//[]

2、赋予空值

let a = [1,2]
a = []
console.log(a)//[]

3、给数组的length赋值为0

let a = [1,2]
a.length = 0
console.log(a)//[]