如何使用 JavaScript 在页面刷新时保持本地存储值？

Question

I am trying to create a click counter using HTML & JavaScript and I want to retain the value of the number after the page is refreshed.

I understand the fact that I have to use local storage for that and I have managed to store the value and display it after the page is refreshed but when I click on the button again, it starts the count from 0 and I do not know how to solve this issue. I want it to retain the value and continue counting even if the page is refreshed.

HTML Code:

   <div>
      <p id="display">0</p>
      <button onclick="increase()">increase</button>
      <button onclick="decrease()">decrease</button>
    </div>

JavaScript Code:

let display=document.getElementById("display")
    let count = 0
    
    function increase(){
        count=count+1
        display.textContent=count
        localStorage.setItem("count", JSON.stringify(count))
        
    }
    display.textContent=localStorage.getItem("count")
    
    
    
    function decrease(){
        count=count-1
        display.textContent=count
    }

Answer 1

let display=document.getElementById("display");
    

let count = localStorage.getItem("count") ? +localStorage.getItem("count") : 0;

    function increase(){
        count=count+1
        display.textContent=count
        localStorage.setItem("count", JSON.stringify(count))
        
    }
    display.textContent=localStorage.getItem("count")
    
    
    
    function decrease(){
        count=count-1
        display.textContent=count
    }

try above snippet.

Answer 2

let display=document.getElementById("display")
let count = Number(localStorage.getItem("count")) // here

function increase(){
    count=count+1
    display.textContent=count
    localStorage.setItem("count", JSON.stringify(count))
    
}
display.textContent = count // and here



function decrease(){
    count=count-1
    display.textContent=count
}

I updated two lines of your code which is commented.

You have to set count variable first with value from localStorage .

Answer 3

when window load get the count value from local storage and init the count variable after that display that count value

const display = document.getElementById("display");

let count = 0;

window.onload = () => {
  count = localStorage.getItem("count")
    ? JSON.parse(localStorage.getItem("count"))
    : 0;
  display.textContent = count;
};

function increase() {
  count = count + 1;
  display.textContent = count;
  localStorage.setItem("count", JSON.stringify(count));
}

function decrease() {
  count = count - 1;
  display.textContent = count;
  localStorage.setItem("count", JSON.stringify(count));
}