javascript 本地存储会话存储JSON.parse

Posted 2021-05-03

//set local storage item (must be passed as strings)
// localStorage.setItem('name', 'John');
// localStorage.setItem('age', '30');

//set session storage item
// sessionStorage.setItem('name', 'Beth');

//remove from storage
// localStorage.removeItem('name');

//get from storage
// const name = localStorage.getItem('name');
// const age = localStorage.getItem('age');


// //clear local storage
// localStorage.clear();

// console.log(name, age);

document.querySelector('form').addEventListener('submit', function(e){
  const task = document.getElementById('task').value;

  let tasks;
  if(localStorage.getItem('tasks') === null){
    tasks = [];
  } else {
    tasks = JSON.parse(localStorage.getItem('tasks'));
  }

  tasks.push(task);

  localStorage.setItem('tasks', JSON.stringify(tasks));
  alert('Task saved');
  
  e.preventDefault();
});

const tasks = JSON.parse(localStorage.getItem('tasks'));

tasks.forEach(function(task){
  console.log(task);
}) 

//JSON.parse takes string data and makes it usable as an 
//array with array methods such as forEach.
//Remember that we must use strings when passing 
//things to localStorage and then convert 
//them back when necessary using JSON.parse