promise.catch和promise.then后的then是否会执行

会的

promise.catch和promise.then都会返回一个promise对象，状态为resolve

let a=new Promise(function(resolve,rej){
    rej(4)
}).then(res=>console.log(res),rej=>console.log(rej+1))
console.log(a)

 let a=new Promise(function(resolve,rej){
    rej(4)
}).catch(res=>console.log(res+3))
console.log(a)

 let a=new Promise(function(resolve,rej){
    rej(4)
}).then(res=>console.log(res+1),rej=>{
    console.log(rej+3)
    return 3
}).then(res=>console.log(res+3),rej=>console.log(rej+1))
console.log(a)

输出7，在输出6