总结

1. 自定义事件

    
    


    按钮

2. 拖拽

3. promise

function test(resolve, reject) {
    let random = Math.random()*2
    setTimeout(function(){
        if (random<1) {
            console.log('success');
            resolve('200 OK')
        }else{
            console.log('error')
            reject('随机数为'+random+'>1')
        }
    }, 1000)
}

let p1 = new Promise(test);
let p2 = p1.then(function(res) {
    console.log('成功：'+res)
})
let p3 = p2.catch(function(err) {
    console.log('失败：'+err)
})