index.js

// Design a stack which supports the following operations.

// Implement the CustomStack class:

// CustomStack(int maxSize) Initializes the object with maxSize which is the maximum number of elements in the stack or do nothing if the stack reached the maxSize.
// void push(int x) Adds x to the top of the stack if the stack hasn't reached the maxSize.
// int pop() Pops and returns the top of stack or - 1 if the stack is empty.
// void inc(int k, int val) Increments the bottom k elements of the stack by val.If there are less than k elements in the stack, just increment all the elements in the stack.

//     Example 1:

// Input
// ["CustomStack", "push", "push", "pop", "push", "push", "push", "increment", "increment", "pop", "pop", "pop", "pop"]
// [[3], [1], [2], [], [2], [3], [4], [5, 100], [2, 100], [], [], [], []]
// Output
// [null, null, null, 2, null, null, null, null, null, 103, 202, 201, -1]
// Explanation
// CustomStack customStack = new CustomStack(3); // Stack is Empty []
// customStack.push(1);                          // stack becomes [1]
// customStack.push(2);                          // stack becomes [1, 2]
// customStack.pop();                            // return 2 --> Return top of the stack 2, stack becomes [1]
// customStack.push(2);                          // stack becomes [1, 2]
// customStack.push(3);                          // stack becomes [1, 2, 3]
// customStack.push(4);                          // stack still [1, 2, 3], Don't add another elements as size is 4
// customStack.increment(5, 100);                // stack becomes [101, 102, 103]
// customStack.increment(2, 100);                // stack becomes [201, 202, 103]
// customStack.pop();                            // return 103 --> Return top of the stack 103, stack becomes [201, 202]
// customStack.pop();                            // return 202 --> Return top of the stack 102, stack becomes [201]
// customStack.pop();                            // return 201 --> Return top of the stack 101, stack becomes []
// customStack.pop();                            // return -1 --> Stack is empty return -1.

// Constraints:

// 1 <= maxSize <= 1000
// 1 <= x <= 1000
// 1 <= k <= 1000
// 0 <= val <= 100
// At most 1000 calls will be made to each method of increment, push and pop each separately.

// Solution

const CustomStack = function (maxSize) {
    this.maxSize = maxSize;
    this.stack = []
};

CustomStack.prototype.push = function (x) {
    if (this.stack.length === this.maxSize) return
    this.stack.push(x)
};

CustomStack.prototype.pop = function () {
    const top = this.stack.pop()
    return top ? top : -1
};

CustomStack.prototype.increment = function (k, val) {
    for (let i = 0; i < k; i++) {
        if (this.stack[i]) this.stack[i] = this.stack[i] + val;
    }
};