Javascript NodeJS 导出变量
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NodeJS export variable
提问by mdv
I am writing a nodejs moduleand I need to pass variable data from the main file to the functions, I am doing this:
我正在编写一个nodejs 模块，我需要将变量数据从主文件传递给函数，我这样做：
var region;
var api_key;
exports.region = region;
exports.api_key = api_key;
module.exports = {
getSummonerId: function(sum, callback) {
var summoners = {};
var summoner = sum.replace(/\s+/g, '');
request("https://na.api.pvp.net/api/lol/"+region+"/v1.4/summoner/by-name/"+summoner+"?api_key="+api_key, function(error, response, body) {
summoners[summoner] = JSON.parse(body);
callback(summoners[summoner][summoner].id);
});
}
}
And in the main file:
在主文件中：
var lol = require('./apiwrapper.js');
lol.api_key = "example";
lol.region = "las";
lol.getChampions(function(data) {
console.log(data);
})
But from apiwrapper.jsthose two variables value is always "undefined".
但是从apiwrapper.js这两个变量的值总是“ undefined”。
Can some point me in the right direction?
有人能指出我正确的方向吗？
Thanks in advance.
提前致谢。
回答by Felix Kling
The value that is imported to the other module is module.exports. So, what you assign to module.exportsis exported. Whatever was assigned earlier to it is lost.
导入到另一个模块的值为module.exports。因此，您分配给的内容module.exports已导出。之前分配给它的任何东西都丢失了。
The relation between module.exportsand exportsis that they refer to the same object initially:
module.exports和之间的关系exports是它们最初指的是同一个对象：
var exports = module.exports = {};
So, assigning a property to either of them mutates the same object. However, you are assigning a new object to module.exports, so now both of them reference different objects.
因此，将属性分配给它们中的任何一个都会改变同一个对象。但是，您正在为 分配一个新对象module.exports，因此现在它们都引用了不同的对象。
A simple solution is to assign the new object to exportsas well and then assign the other properties:
一个简单的解决方案是将新对象exports也分配给，然后分配其他属性：
exports = module.exports = {...};
exports.region = region;
If you want to keep the order of the statements, then you have to extend the default exports object, instead of creating a new one:
如果你想保持语句的顺序，那么你必须扩展默认的导出对象，而不是创建一个新的对象：
Object.assign(exports, { ... });
回答by Rana
Why not using:
为什么不使用：
module.exports = {
region: my_region,
api_key: my_api_key,
getSummonerId: function(sum, callback) {
var summoners = {};
var summoner = sum.replace(/\s+/g, '');
request("https://na.api.pvp.net/api/lol/"+region+"/v1.4/summoner/by-name/"+summoner+"?api_key="+api_key, function(error, response, body) {
summoners[summoner] = JSON.parse(body);
callback(summoners[summoner][summoner].id);
});
}
}
in your case, "module.exports" is overwriting the previously exported variables. Which is the reason you are getting undefined for those.
在您的情况下，“module.exports”正在覆盖之前导出的变量。这就是您对这些未定义的原因。
