Why is pop faster than shift?

Question

Douglas Crockford, in JavaScript: The Good Parts, states that \"shift is usually much slower than pop\". jsPerf confirms this. Does anyone know why this is the case

Answer 1

Because shift() reindex array so the shift method is very slow on large array.

var array = [];
for(var i = 0;i< 1000000;i++){
    array.push(i)
}
var start = new Date().getTime()
for(var i = 0; i< 100000; i++){
 array.shift();
}
var duration = new Date().getTime() - start;// duration is so large, greater than 3 minutes

But the duration is just 8ms when using linked-queue

var LQueue = require('linked-queue')
var queue = new LQueue()
for(var i = 0;i< 1000000;i++){
    queue.enqueue(i);
}
console.log("Queue length:"+ queue.length);
var start = new Date().getTime()
queue.dequeueAll(function(data){
})
var end  = new Date().getTime();
console.log("Time:" + (end - start));// 8 ms
console.log("Queue length:"+ queue.length);