Stack Implementation in JavaScript

dataStructures.js

class Stack { 
  constructor () { 

    this.state = { 
      storage: '', 
      count: 0, 
      mostRecent: ''
    }
  };

  push (value) {
    this.state.storage = this.state.storage + '***' + value;
    this.state.count = this.updateCount(1);
    this.state.mostRecent = value; 
  };

  findDelimiter (value) { 
    return this.state.storage.lastIndexOf(value);
  };

  sliceString (delimiter, index) { 
    return this.state.storage.slice(delimiter + 3, index);
  };

  updateCount (amount) { 
    return this.state.count + amount;
  };

  pop () {
    const str = this.sliceString(this.findDelimiter('***'));
    this.state.storage = this.state.storage.substring(0, this.findDelimiter('***'));
    this.state.count = this.updateCount(-1);
    this.state.mostRecent = this.sliceString(this.findDelimiter('***'), this.state.storage.length)
    return str;
  };

  count () { 
    return this.state.count;
  };

  peek () { 
    return this.state.mostRecent;
  };
} 

const myStack = new Stack();