Min Stack.js

/*Design a stack that supports push, pop, top, and retrieving the minimum element in constant time.

push(x) -- Push element x onto stack.
pop() -- Removes the element on top of the stack.
top() -- Get the top element.
getMin() -- Retrieve the minimum element in the stack.

Example:
MinStack minStack = new MinStack();
minStack.push(-2);
minStack.push(0);
minStack.push(-3);
minStack.getMin();   --> Returns -3.
minStack.pop();
minStack.top();      --> Returns 0.
minStack.getMin();   --> Returns -2.*/

/**
 * initialize your data structure here.
 */
var MinStack = function() {
    this.stack = []
};

/** 
 * @param {number} x
 * @return {void}
 */
MinStack.prototype.push = function(x) {
    this.stack.unshift(x)
};

/**
 * @return {void}
 */
MinStack.prototype.pop = function() {
    this.stack.splice(0,1)
};

/**
 * @return {number}
 */
MinStack.prototype.top = function() {
    return this.stack[0]
};

/**
 * @return {number}
 */
MinStack.prototype.getMin = function() {
    var min = this.stack[0]
    for(var i=0; i<this.stack.length; i++){
        if(min > this.stack[i])
            min = this.stack[i]
    }
    return min
};

/** 
 * Your MinStack object will be instantiated and called as such:
 * var obj = Object.create(MinStack).createNew()
 * obj.push(x)
 * obj.pop()
 * var param_3 = obj.top()
 * var param_4 = obj.getMin()
 */