Sorting Integers with two stacks in javascript

sorting_integers_with_two_stacks.js

function Stack() {
    this.data = []
}

Stack.prototype.pop = function () {
    return this.data.pop()
}
Stack.prototype.push = function (item) {
    this.data.push(item)
}
Stack.prototype.peek = function () {
    return this.data[this.data.length - 1]
}

Stack.prototype.toString = function() {
    return this.data.toString()
}

Stack.prototype.isEmpty = function() {
    return this.data.length === 0
}

var stack1 = new Stack()
var stack2 = new Stack()
var temp

stack1.push(12)
stack1.push(34)
stack1.push(15)
stack1.push(1)

console.log(stack1.toString())

while(!stack1.isEmpty()) {
    temp = stack1.pop()
    while(!stack2.isEmpty() && temp < stack2.peek()) {
        stack1.push(stack2.pop())
    }
    stack2.push(temp)
}

console.log(stack2.toString())