[英]Promises, how to pass variable into .then function
Hello this is a question to help me understand how Promises .then
returns work. 您好,这是一个帮助我了解Promises .then
返还工作方式的问题。 The question is: how can I scoped variables to the second .then chained function? 问题是:如何将变量的作用域限定为第二个.then链接函数?
Here is a jsbin http://jsbin.com/xacuna/edit?js,output 这是一个jsbin http://jsbin.com/xacuna/edit?js,输出
I can access the global variables, and pass in the scoped variables to the first then, but not after. 我可以访问全局变量,然后将范围变量传递给第一个变量,但不能传递给后面的变量。
let innerReturnFunction = (res, myName) => {
/* this works */
console.log(`hi from inner name: ${myName}`)
return res
}
let getInnerFuncVariable = () => {
var myName = 'arturo'
return fetch('https://httpbin.org/get')
.then(function (res) {
myName = 'Bob'
return innerReturnFunction(res, myName);
})
.then(function (res, myName) {
/* doesn't work, how can I access myName */
console.log(`in first then ${res.url}, ${myName}`)
});
}
getInnerFuncVariable().then(function(res, myName) {
/* how can I access myName */
console.log(`last called ${myName}`)
})
as you are using ES2015 - easy solution uses object Shorthand property names and Object destructuring 使用ES2015时-简单的解决方案使用对象简写属性名称和对象分解
let innerReturnFunction = ({res, myName}) => {
/* this works */
console.log(`hi from inner name: ${myName}`);
return {res, myName}; // return an object
}
let getInnerFuncVariable = () => {
var myName = 'arturo';
return fetch('https://httpbin.org/get')
.then(function(res) {
myName = 'Bob'
return innerReturnFunction({res, myName});
})
.then(function({res, myName}) {
console.log(`in first then ${res.url}, ${myName}`);
return {res, myName};// ADD THIS!!
});
}
getInnerFuncVariable().then(function({res, myName}) {
console.log(`last called ${myName}`)
})
When I came across this answer, I was trying to do this: 当我遇到这个答案时,我正在尝试这样做:
for (key in updateDict)
{ if ( ! key.startsWith("__"))
{ var updateID = updateDict[key].id;
var updateNewValue = updateDict[key].newValue;
//store give the function call the ability to store the current value of key
var storeAndDeleteKey = function(key, updateID, updateNewValue)
{ return atStore.update({"id":updateID}, updateNewValue))
.then
( (docs) =>
{ results[key] = docs;
delete updateDict[key];
}
);
}
//put the function with the current value of key into the Promise.all list
dataAccessPromiseList.push
( storeAndDeleteKey(key, updateID, updateNewValue)
)
}
}
if (dataAccessPromiseList.length > 0) dataAccessPromise = Promise.all(dataAccessPromiseList);
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