array operations performance

arrOpsPerf.js

var arrsize=100000
// time cost for array constructing
var i = 0
var ar = [] // literal notation
var arr = new Array(arrsize) // new length defined

i = 0
console.time("Literal notation with assigning directly")
while(i<arrsize){
  ar[i] = i
  i++
}
console.timeEnd("Literal notation with assigning directly")

i = 0
ar = []
console.time("Literal notation with push()")
while(i<arrsize){
  ar.push(i)
  i++
}
console.timeEnd("Literal notation with push()")


ar = []
console.time("Literal notation with unshift()")
while(i>=0){
  ar.unshift(i)
  i--
}
console.timeEnd("Literal notation with unshift()")

i = 0
ar = []
console.time("Literal notation with push()")
while(i<arrsize){
  ar.push(i)
  i++
}
console.timeEnd("Literal notation with push()")


console.time("Literal notation with shift()")
while(i>=0){
  ar.shift()
  i--
}
console.timeEnd("Literal notation with shift()")


i = 0
ar = []
ar.length = arrsize
console.time("Literal notation with declaring length first")
while(i<arrsize){
  ar[i] = i
  i++
}
console.timeEnd("Literal notation with declaring length first")

i = 0
console.time("Using new with length defined")
while(i<arrsize){
  arr[i] = i
  i++
}
console.timeEnd("Using new with length defined")

i = 0
arr = new Array(arrsize)
console.time("Using new with length defined again")
while(i<arrsize){
  arr[i] = i
  i++
}
console.timeEnd("Using new with length defined again")

i = 0
arr = new Array(arrsize)
console.time("simply iterating")
while(i<arrsize){
  i++
}
console.timeEnd("simply iterating")