这似乎是一个愚蠢的问题,但我是这个主题的新手。我正在研究节点js上的promises。我想将参数传递给promise函数。但是我无法理解。
someModule.someFunction.then(username, password,function(uid) {
/*stuff */
}
,功能类似于
var someFunction = new Promise(username, password, function(resolve, reject) {
/*stuff using username, password*/
if ( /* everything turned out fine */ ) {
resolve("Stuff worked!");
} else {
reject(Error("It broke"));
}
});
答案 0 :(得分:129)
将你的Promise包裹在一个函数中,否则它将立即开始工作。另外,您可以将参数传递给函数:
var someFunction = function(username, password) {
return new Promise(function(resolve, reject) {
/*stuff using username, password*/
if ( /* everything turned out fine */ ) {
resolve("Stuff worked!");
} else {
reject(Error("It broke"));
}
});
}
然后,使用它:
someModule.someFunction(username, password).then(function(uid) {
/* stuff */
})
<强> ES6:强>
const someFunction = (username, password) => {
return new Promise((resolve, reject) => {
/*stuff using username, password*/
if ( /* everything turned out fine */ ) {
resolve("Stuff worked!");
} else {
reject(Error("It broke"));
}
});
};
使用:
someModule.someFunction(username, password).then(uid => {
/* stuff */
});
答案 1 :(得分:3)
更短
var foo = (user, pass) =>
new Promise((resolve, reject) => {
if (/* condition */) {
resolve("Fine");
} else {
reject("Error message");
}
});
foo(user, pass).then(result => {
/* process */
});
答案 2 :(得分:1)
您可以在带参数的函数中返回您的承诺。像这样:
function someFunction(username, password) {
return new Promise((resolve, reject) => {
// Do something with the params username and password...
if ( /* everything turned out fine */ ) {
resolve("Stuff worked!");
} else {
reject(Error("It didn't work!"));
}
});
}
someFunction(username, password)
.then((result) => {
// Do something...
})
.catch((err) => {
// Handle the error...
});
答案 3 :(得分:0)
您可以使用.bind()将参数( this )传递给函数。
var someFunction =function(resolve, reject) {
/* get username, password*/
var username=this.username;
var password=this.password;
if ( /* everything turned out fine */ ) {
resolve("Stuff worked!");
} else {
reject(Error("It broke"));
}
}
var promise=new Promise(someFunction.bind({username:"your username",password:"your password"}));
答案 4 :(得分:0)
我用这个..
let verifyEmail = (email) => new Promise((resolve, rejected) => {
let rsp = {isRepeated:false}
let sql = `select id from users where email='${email}' `
try{
db.query(sql, (err,result)=>{
if(!err){
if(result.length > 0){
rsp = {isRepeated:true}
}
}
})
resolve(rsp)
}catch(e){
rejected({ok:false,err:e})
}
})