新建一个长度为100的数组, 并且每一项都是1

1. fill() 填充

   let arr = []
   arr.length = 100
   
   // 或arr = Array(100)
   arr.fill(1)
   

2. 循环

   let arr = []
   for(let i = 0; i < 100; i++){
   	arr[i] = 1
   }
   

3. 字符串repeat

   let arr = [...'1'.repeat(100)].map(Number)
   
   

4. 同样字符串 padStart/ padEnd

   let arr = [...'1'.padEnd(100, 1)].map(Number)
   

5. 还有对象(伪数组)的转换, 不过有点多此一举

   let obj = {}
   for(let i = 0; i < 100; i++){
   	obj[i] = 1
   }
   obj.length = 100
   let arr = Array.from(obj)
   

6. Array.keys() + fill

   let arr = Array.from(new Array(100).keys()).fill(1);
   

…

感觉都差不多