flatten

function flatten(array){
arr=array
let arr1=[]
var a,count=0
for(i=0;i<arr.length;i++)
{
if(arr[i].length==undefined){
arr1.push(arr[i])
}
else
{
[a,...rest]=arr[i]
arr1.push(a)
for(j=0;j<rest.length;j++)
{
 arr1.push(rest[j])
}
}
}
console.log(arr1)
}
arr5=flatten([[1,[2,3],5],6,4])