Implementation of stack

We need to implement the following functions ：

push()    Stack method

pop()      Stack method

top()        Get stack top value

size()      Get the number of elements of the stack

clear()    Empty stack

class Stack {
  constructor () {
    //  Store stack data 
    this.data = []

    //  Number of recorded data 
    this.count = 0
  }

  //  Stack method 
  push (item) {
    // this.data.push(item)
    // this.data[this.data.length] = item

    this.data[this.count] = item
    this.count++
  }

  //  Stack method 
  pop () {
    if (this.isEmpty()) {
      console.log(' The stack is empty. ')
      return
    }

    const temp = this.data[this.count - 1]
    delete this.data[--this.count]
    return temp
  }

  //  Check if the stack is empty 
  isEmpty () {
    return this.count === 0
  }

  //  Get stack top element 
  top () {
    if (this.isEmpty()) {
      console.log(' The stack is empty. ')
      return
    }

    return this.data[this.count - 1]
  }

  //  Get the number of elements 
  size () {
    return this.count
  }

  //  Empty stack 
  clear () {
    this.data = []
    this.count = 0
  }
}

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