为什么我的代码在控制台中显示“Uncaught SyntaxError: Identifier 'calculator' has already been declared'？

Question

I tried making a calculator, but checking it at this stage, it's displaying some syntax error.

Please I need help. How can I correct this? There is a class of calculator there and I represented it with the 'new' word. This is vanilla JavaScript. Tried calling the function, but it kept on giving me the error in my console. Please could someone help me?

class calculator {
  constructor(previousOperandTextElement, currentOperandTextElement) {
    this.perviousOperandTextElement = previousOperandTextElement
    this.currentOperandTextElement = currentOperandTextElement
    this.clear()
  }
    
  clear() {
    this.currentOperand = ''
    this.previousOperand = ''
    this.operation = undefined
  }
    
  delete() {
  }

  appendNumber(number) {
    this.currentOperand = number
  }
    
  chooseOperation(operation) {   
  }
    
  compute() {
  }

  updateDisplay() {
    this.currentOperandTextElement.innerText = this.currentOperand;
  }
}
    
const numberButtons = document.querySelectorAll('[data-number]')
const operationButtons = document.querySelectorAll('[data-operation]')
const equalsButton = document.querySelector('[data-equals]')
const deleteButton = document.querySelector('[data-delete]')
const allclearButton = document.querySelector('[data-all-clear]')
const previousOperandTextElement = document.querySelector('[data-previous-operand]')
const currentOperandTextElement = document.querySelector('[data-current-operand]')
        
const calculator = new calculator(previousOperandTextElement, currentOperandTextElement)

numberButtons.forEach(button => {
  button.addEventListener('click', () => {
    calculator.appendNumber(button.innerText)
    calculator.updateDisplay()
  })
})

Answer 1

Identifier 'calculator' has already been declared' means you've used name 'calculator' twice, in your code - class is named 'calculator' and constant for calculator object is also 'calculator'.

Change class name to 'Calculator':

class Calculator {
  constructor(previousOperandTextElement, currentOperandTextElement) {
    this.perviousOperandTextElement = previousOperandTextElement
    this.currentOperandTextElement = currentOperandTextElement
    this.clear()
  }

  clear() {
    this.currentOperand = ''
    this.previousOperand = ''
    his.operation = undefined
  }

  delete() {

  }

  appendNumber(number) {
   this.currentOperand = number
  }

  chooseOperation(operation) {

  }

  compute() {

  }

  updateDisplay() {
    this.currentOperandTextElement.innerText = this.currentOperand;
  }
}



const numberButtons = document.querySelectorAll('[data-number]')
const operationButtons = document.querySelectorAll('[data-operation]')
const equalsButton = document.querySelector('[data-equals]')
const deleteButton = document.querySelector('[data-delete]')
const allclearButton = document.querySelector('[data-all-clear]')
const previousOperandTextElement = document.querySelector('[data-previous-operand]')
const currentOperandTextElement = document.querySelector('[data-current-operand]')
    
// error was here
const calculator = new Calculator(previousOperandTextElement, currentOperandTextElement)



numberButtons.forEach(button => {
  button.addEventListener('click', () => {
    calculator.appendNumber(button.innerText)
    calculator.updateDisplay()
  })
})

PS always name your classes with upper case first letter, that is the convention