2. Promise passing value

The status of the promise can be passed on, but the value can only be received once, the effect is as follows

        new Promise((resolve,reject)=>{
            console.log("第一层")
            resolve("数据a")
        }).then(suc=>{ console.log(suc)}, //数据a
        _=>{ console.log("then1") 
        }).then(suc=>{console.log(suc)},//并没有输出"数据a"，而是输出undefined
        _=>{console.log("then2Fail")
        })

So how do you continue to pass the value? Use the change state learned in the previous article to pass the value, use the following

        new Promise((resolve,reject)=>{
            console.log("第一层")
            resolve("数据a")
        }).then(suc=>{ console.log(suc)  //数据a      
        return Promise.resolve(suc)},
        _=>{ console.log("then1") 
        }).then(suc=>{console.log(suc)},//数据a
        _=>{console.log("then2Fail")
        })