promise

function asyncFun(a,b,cb) {
    setTimeout(function(){
        cb(a+b)
    },200)
}

asyncFun(1,2,function(result){
    console.log(result)
})

console.log(2)
// 先返回2再返回3

// promise 产生的原因
function asyncFun(a,b,cb) {
    setTimeout(function(){
        cb(a+b)
    },200)
}

asyncFun(1,2,function(result){
    if (result>2) {
        asyncFun(result,2,function(result){
            if (result>4) {
                asyncFun(result,2,function(result){
                    if (result>4) {
                        console.log(‘ok‘)
                    }
                })
            }
        })
    }
})

console.log(2)//2之后才是ok

function asyncFun(a,b) {
    return new Promise(function(resolve,reject){

        if (typeof a!==‘number‘||typeof b!==‘number‘) {
            reject(new Error(‘no number‘))
        }

        setTimeout(function(){
            resolve(a+b)
        },200)
    })
}

asyncFun(1,‘a‘)
    .then(function(result){
        if (result>2) {
            return asyncFun(result,2)
        }
}).then(function(result){
    if (result>4) {
        console.log(‘ok‘)
    }
}).catch(function(error){
    console.log(‘second‘+error)
})//secondError: no number

class User{
    constructor(name,password){
        this.name = name;
        this.password = password
    }

    validateName(){
        let name = this.name
        return new Promise(function(resolve,reject){
            setTimeout(function(){
                if (name === ‘Leo‘) {
                    resolve(‘success‘)
                }else{
                    reject(‘error‘)
                }                
            })

        })
    }
    validatePwd(){
        let password = this.password
        return new Promise(function(resolve,reject){
            setTimeout(function(){
                if (password === ‘123‘) {
                    resolve(‘success‘)
                }else{
                    reject(‘error‘)
                }                
            })

        })
    }
}
const user = new User(‘Leo‘,‘123‘);
user.validateName().then(function(result){
    return user.validatePwd()
}).then(function(result){
    console.log(‘登录成功‘)
}).catch(function(err){
    console.log("err")
})
// 登录成功

class User{
    constructor(name,password){
        this.name = name;
        this.password = password
    }

    validateName(){
        let name = this.name
        return new Promise(function(resolve,reject){
            setTimeout(function(){
                if (name === ‘Leo‘) {
                    resolve(‘success‘)
                }else{
                    reject(‘error‘)
                }                
            })

        })
    }
    validatePwd(){
        let password = this.password
        return new Promise(function(resolve,reject){
            setTimeout(function(){
                if (password === ‘123‘) {
                    resolve(‘success‘)
                }else{
                    reject(‘error‘)
                }                
            })

        })
    }
}
const user = new User(‘Leo‘,‘123‘);
user.validateName().then(function(result){
    return ‘Ok‘
})
// 如果不是promise的话会自己封装成下面这种promise方法
// Promise.resolve(‘ok‘)
// var promise = new Promise(function(resolve,reject){
//     resolve(‘ok‘)
// })
    .then(function(result){
        console.log(result)
    })
// OK

class User{
    constructor(name,password){
        this.name = name;
        this.password = password
    }

    validateName(){
        let name = this.name
        return new Promise(function(resolve,reject){
            setTimeout(function(){
                if (name === ‘Leo‘) {
                    resolve(‘success‘)
                }else{
                    reject(‘error‘)
                }                
            })

        })
    }
    validatePwd(){
        let password = this.password
        return new Promise(function(resolve,reject){
            setTimeout(function(){
                if (password === ‘123‘) {
                    resolve(‘success‘)
                }else{
                    reject(‘error‘)
                }                
            })

        })
    }
}
// const user = new User(‘Leo1‘,‘123‘);
// user.validateName().then(function(result){
//     throw new Error(‘firsterr‘)
//     return user.validatePwd()
// },function(err){
//     console.log(‘seconderr‘)//这是出现错误所调用的
// }).catch(function(err){
//     console.log(err)
// })
// // seconderr

// const user = new User(‘Leo‘,‘123‘);
// user.validateName().then(function(result){
//     throw new Error(‘firsterr‘)
//     return user.validatePwd()
// },function(err){
//     console.log(‘seconderr‘)//这是出现错误所调用的
// }).catch(function(err){
//     console.log(err)
// })
// firsterr

// const user = new User(‘Leo‘,‘1234‘);
// user.validateName().then(function(result){
//     throw new Error(‘firsterr‘)
//     return user.validatePwd()
// },function(err){
//     console.log(‘seconderr‘)//这是出现错误所调用的
// }).catch(function(err){
//     console.log(err)
//     return user.validatePwd()
// }).then(function(result){
//     console.log(result)
// })
// 密码正确的话就显示firsterr  不正确的话显示  firsterr  error


const user = new User(‘Leo‘,‘1234‘);
user.validateName().then(function(result){
    throw new Error(‘firsterr‘)
    return user.validatePwd()
},function(err){
    console.log(‘seconderr‘)//这是出现错误所调用的
}).catch(function(err){
    console.log(err)
    return user.validatePwd()
}).then(function(result){
    console.log(result)
}).catch(function(err){
    
})

function asyncFun(a,b) {
    return new Promise(function(resolve,reject){

        if (typeof a!==‘number‘||typeof b!==‘number‘) {
            reject(new Error(‘no number‘))
        }

        setTimeout(function(){
            resolve(a+b)
        },200)
    })
}
// 只要一个有错误就不会执行promise
// var promise = Promise.all([asyncFun(1,2),asyncFun(3,4),asyncFun(5,6)]);
// promise.then(function(result){
//     console.log(result)//[ 3, 7, 11 ]
// })

// var promise = Promise.race([asyncFun(1,2),asyncFun(3,4),asyncFun(5,6)]);
// promise.then(function(result){
//     console.log(result)//[ 3 ]
// })

// var promise = Promise.race([asyncFun(1,‘2‘),asyncFun(3,4),asyncFun(5,6)]);
// promise.then(function(result){
//     console.log(result)//[ 3 ]
// })
// no number