script.js

const tasks = [];
//[1,2,3], [{task:''},{task:'test'}]

//' abc  '.trim() -> 'abc'
//string,number,boolean,undefind,null,array,object
function addTask(){
    console.log('add task')
    const taskInput = document.getElementById('taskInput');
    const priorityInput = document.getElementById('priorityInput');
    const task = taskInput.value.trim();
    const priority =parseInt(priorityInput.value);
    //不管是input，select，textarea，它们的value都是string, '1'转化成数字用parseInt
    console.log('task',task)
    if(!task){
        alert('Please enter a task.');
        return;
    }
    let importance = '';
    if(priority <= 2){
        importance = 'high'
    }else if(priority === 3){
        importance = 'medium'
    }else {
        importance = 'low'
    }
    const newTask = {
        'task': task,
        'priority':priority,
        'importance':importance
    }
    tasks.push(newTask)
    console.log('tasks',tasks)
    taskInput.value = '';
    renderTasks();
}
function renderTasks(){
    const arr = ['a','b','c'];
    console.log('arr length',arr.length)// max index = arr.length - 1
    const taskList = document.getElementById('taskList');
    taskList.innerHTML = '';
    
    for(let i = 0; i < tasks.length; i++){
       const item = tasks[i]//tasks[0]
       const li = document.createElement('li');
       li.className = `task ${item.importance}` //'task ' + item.importance
       li.textContent =`${item.task} (Priority ${item.priority})` 
       taskList.appendChild(li)
    }
}