1.resolve()
使pending状态变成resolved状态
代码：
let p = new Promise((resolve,reject) => {
resolve('ok')
})
console.log(p);
效果:
2.reject()
使pending状态变成rejected状态
代码：
let p = new Promise((resolve,reject) => {
reject('error')
})
console.log(p);
效果:
3.抛出异常
使pending状态变成resolved状态
代码：
let p = new Promise((resolve,reject) => {
throw '出错了'
})
console.log(p);
效果:
