JavaScript/DataStructures/Stack.js at master · akshitagit/JavaScript · GitHub

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export default class Stack {
    constructor() {
        this.items = [];
        this.top = null;
    }

    getTop() {
        if(this.items.length == 0)
            return null;

        return this.top;
    }

    isEmpty() {
        return this.items.length == 0;
    }

    size() {
        return this.items.length;
    }

    push(element) {
        this.items.push(element);
        this.top = element;
    }

    pop() {
        if(this.items){
            if(this.items.length == 1){
                this.top = null;
                return this.items.pop();
            }
            else {
                this.top = this.items[this.items.length - 2];
                return this.items.pop();
            }
        }
        else {
            throw Error("Stack Underflow Exception: The stack is empty.");
        }
    }
}