Node3-3基础API----event(事件触发器)

Posted 2022-09-01 chorkiu

1.基础(on)

// 如果像对象享有事件能力就要集成EventEmitter 
const EventEmitter = require(‘events‘)
//集成EventEmitter类
class CustomEvent extends EventEmitter


// 实例化对象
const ce = new CustomEvent()
//绑定一个事件名
ce.on(‘test‘,()=>
    console.log(‘this is a test‘);
)

setInterval(()=>
    ce.emit(‘test‘)
,500)

运行效果就是不断的执行this is a test

2.传一些参数,基础信息

const EventEmitter = require(‘events‘)

class CustomEvent extends EventEmitter
const ce = new CustomEvent() 

ce.on(‘error‘,(err,time)=>
    console.log(err);
    console.log(time);
    
);

ce.emit(‘error‘,new Error(‘oops!‘),Date.now())

3.执行一次就好了 once(下面即使是像之前on那样操作,也就是每个500毫秒执行一次,可是运行之后也就执行一次而已)

const EventEmitter = require(‘events‘)
class CustomEvent extends EventEmitter

const ce = new CustomEvent()
ce.once(‘test‘,()=>
    console.log(‘test event‘);
    
)
setInterval(()=>
    ce.emit(‘test‘)
,500)

4.移除工作,绑定了一些事件在某些场景下需要移除掉(removeListener  或者 removeAllListener)

const EventEmitter = require(‘events‘)
class CustomEvent extends EventEmitter
function fn1()
    console.log(‘fn1‘);

function fn2()
    console.log(‘fn2‘);

const ce = new CustomEvent()
ce.on(‘test‘,fn1)
ce.on(‘test‘,fn2)
setInterval(()=>
    ce.emit(‘test‘)
,500)
setTimeout(()=>
    // ce.removeListener(‘test‘,fn2)
    // ce.removeListener(‘test‘,fn1)
    //移除所有事件名的事件
    ce.removeAllListeners(‘test‘)
,1500)