I have the following recursive function saved in a file called helpers.js. When it is loaded into the main app.js file using:
var helpers = require('./helpers');
calling it only works partially. The line:
s+=recurseJSON(o[a]);
doesn't get called so the JSON parsing doesn't recurse into nested levels.
I have also tried the following which still doesn't work:
s+=helpers.recurseJSON(o[a]);
If I move the code below into the main app.js file, the recursion works perfectly, obviously changing
recurseJSON: function(o) {...
to
function recurseJSON(o) {..
Your thoughts are appreciated. Here is the whole code:
module.exports = {
recurseJSON: function(o){
var s = '';
for(var a in o){
if (typeof o[a] == 'object'){
s+=a+':';
console.log('JSON>', a, ":");
s+=recurseJSON(o[a]); // This line should recurse but doesn't
}else{
s+=a+':'+o[a]+' ';
console.log('JSON>', a, ":", o[a]);
}//end if
}//end for
return s;
}
};
PS: Credit to Recursively parsing JSON for the original recursive code.
While leaving the export statement like this:
module.exports = {
recurseJSON: function(o){
...
}
};
You can call the function recursively using the statement s+=this.recurseJSON(o[a]), but only assuming that the only way you invoke the recurseJSON() function outside the file is
helpers.recurseJSON(obj)
so that recurseJSON() is the calling member of helpers, making the this in recurseJSON() refer to helpers.
If you cannot guarantee this, then the correct way to invoke it, which is more verbose, is
s+=module.exports.recurseJSON(o[a])
Update
Another simpler solution is to just name the function you're exporting:
module.exports = {
recurseJSON: function recurseJSON(o){
...
}
};
Then you can just use s+=recurseJSON(o[a]) like you had before.
Related
Ive node moudle which i need to export two functions and get to both of the function a parameter arg1,I try with the following I got error,what am I doing wrong here ?
UPDATE
Ive two method inside module
1. I need to expose it outside and to call it explicit from other
module with parameter
like
require('./controller/module')(functionName1)(parameter);
another function(functionName2) in this module which I need to call it explicit with two parameter ,how should I do it right?
It is not very clear what you want to do, but i think you want something like that:
module.exports = function (arg1) {
return {
server: function (params1) {
//do something with arg1 and params1
},
proc: function (params2) {
//do something with arg1 and params2
}
}
};
And using the module:
var arg1 = 'whatever'
var myMod = require('myMod')(arg1);
myMod.server();
myMod.proc();
Option 2
If i look at your new example
require('./controller/module')(functionName1)(parameter);
you need module that exports a function that returns another function (Higher Order Function).
So for example:
module.exports = function(functionName1) {
if(functionName1 === 'server'){
return function server(parameter){
//do your stuff here
}
}
if(functionName1 === 'proc'){
return function proc(parameter){
//do your stuff here
}
}
};
I need to use bluebird in my code and I have no idea how to use it. My code contains nested loops. When the user logs in, my code will run. It will begin to look for any files under the user, and if there are files then, it will loop through to get the name of the files, since the name is stored in a dictionary. Once it got the name, it will store the name in an array. Once all the names are stored, it will be passed along in res.render().
Here is my code:
router.post('/login', function(req, res){
var username = req.body.username;
var password = req.body.password;
Parse.User.logIn(username, password, {
success: function(user){
var Files = Parse.Object.extend("File");
var object = [];
var query = new Parse.Query(Files);
query.equalTo("user", Parse.User.current());
var temp;
query.find({
success:function(results){
for(var i=0; i< results.length; i++){
var file = results[i].toJSON();
for(var k in file){
if (k ==="javaFile"){
for(var t in file[k]){
if (t === "name"){
temp = file[k][t];
var getname = temp.split("-").pop();
object[i] = getname;
}
}
}
}
}
}
});
console.log(object);
res.render('filename', {title: 'File Name', FIles: object});
console.log(object);
},
error: function(user, error) {
console.log("Invalid username/password");
res.render('logins');
}
})
});
EDIT:The code doesn't work, because on the first and second console.log(object), I get an empty array. I am suppose to get one item in that array, because I have one file saved
JavaScript code is all parsed from top to bottom, but it doesn't necessarily execute in that order with asynchronous code. The problem is that you have the log statements inside of the success callback of your login function, but it's NOT inside of the query's success callback.
You have a few options:
Move the console.log statements inside of the inner success callback so that while they may be parsed at load time, they do not execute until both callbacks have been invoked.
Promisify functions that traditionally rely on and invoke callback functions, and hang then handlers off of the returned value to chain the promises together.
The first option is not using promises at all, but relying solely on callbacks. To flatten your code you will want to promisify the functions and then chain them.
I'm not familiar with the syntax you're using there with the success and error callbacks, nor am I familiar with Parse. Typically you would do something like:
query.find(someArgsHere, function(success, err) {
});
But then you would have to nest another callback inside of that, and another callback inside of that. To "flatten" the pyramid, we make the function return a promise instead, and then we can chain the promises. Assuming that Parse.User.logIn is a callback-style function (as is Parse.Query.find), you might do something like:
var Promise = require('bluebird');
var login = Promise.promisify(Parse.User.logIn);
var find = Promise.promisify(Parse.Query.find);
var outerOutput = [];
return login(yourArgsHere)
.then(function(user) {
return find(user.someValue);
})
.then(function(results) {
var innerOutput = [];
// do something with innerOutput or outerOutput and render it
});
This should look familiar to synchronous code that you might be used to, except instead of saving the returned value into a variable and then passing that variable to your next function call, you use "then" handlers to chain the promises together. You could either create the entire output variable inside of the second then handler, or you can declare the variable output prior to even starting this promise chain, and then it will be in scope for all of those functions. I have shown you both options above, but obviously you don't need to define both of those variables and assign them values. Just pick the option that suits your needs.
You can also use Bluebird's promisifyAll() function to wrap an entire library with equivalent promise-returning functions. They will all have the same name of the functions in the library suffixed with Async. So assuming the Parse library contains callback-style functions named someFunctionName() and someOtherFunc() you could do this:
var Parse = Promise.promisifyAll(require("Parse"));
var promiseyFunction = function() {
return Parse.someFunctionNameAsync()
.then(function(result) {
return Parse.someOtherFuncAsync(result.someProperty);
})
.then(function(otherFuncResult) {
var something;
// do stuff to assign a value to something
return something;
});
}
I have a few pointers. ... Btw tho, are you trying to use Parse's Promises?
You can get rid of those inner nested loops and a few other changes:
Use some syntax like this to be more elegant:
/// You could use a map function like this to get the files into an array of just thier names
var fileNames = matchedFiles.map(function _getJavaFile(item) {
return item && item.javaFile && item.javaFile.name // NOT NULL
&& item.javaFile.name.split('-')[0]; // RETURN first part of name
});
// Example to filter/retrieve only valid file objs (with dashes in name)
var matchedFiles = results.filter(function _hasJavaFile(item) {
return item && item.javaFile && item.javaFile.name // NOT NULL
&& item.javaFile.name.indexOf('-') > -1; // and has a dash
});
And here is an example on using Parse's native promises (add code above to line 4/5 below, note the 'then()' function, that's effectively now your 'callback' handler):
var GameScore = Parse.Object.extend("GameScore");
var query = new Parse.Query(GameScore);
query.select("score", "playerName");
query.find().then(function(results) {
// each of results will only have the selected fields available.
});
What's the best way to pass thisArg to a require()d module?
I want to do something like this:
index.js
function Main(arg) {
return {
auth: auth,
module: require('/some/module')
}
}
module.js
module.exports = {
someMethod: function() {...}
}
Then, in my code somewhere I call Main(), which returns the object.
So Main().auth exists, cool. But how do I access it from Main().module?
The thisArg in Main().module.someMethod() points to the module itself.. but I need the parent.
Is there any way to do this without using new keyword, functions and prototypes?
EDIT:
Thanks for all the answers guys! Some additional info:
Main() is the module what I wanna require() and use in my app. The "module" Main tries to import is actually just sub functionality of Main, it's just a part of code which I moved to a separate "module" to better organize the code.
So a better example would be:
function RestApi(param) {
return {
common_param: param,
commonFunc: function() {...}
endpoint1: require('/some/module'),
endpoint2: require('/some/module2'),
endpoint3: require('/some/module3')
}
}
And my app would use it like this:
RestApi = require('./RestApi')
RestApi().endpoint1.someHTTPCall(...)
But inside someHTTPCall(), both "common_param" and "commonFunc" should be accessible via thisArg, like this.commonFunc().
So this is kinda a general question, how do you merge multiple modules using require() properly, so "this" would point to the right object (i.e.: the parent)
I know this could be achieved using Function.prototype and inheritance, just would like to know if there is a simpler way.
The best I found so far is something like this:
var _ = require('lodash');
function Module(auth) {
this.auth = auth || {};
}
Module.prototype = {
endpoint1: function() { return _.extend(require('./endpoint1'),{auth: this.auth, commonFunc: commonFunc})}
}
function commonFunc() {...}
However, this is not ideal, since RestApi.endpoint1() would create a new the object on every call.
Is there a better way to handle this?
Thanks in advance!
Create own "require" module with auth param and allways use it.
project/module/require2.js
module.exports = function(path, auth){
if (!check(auth))
return null
return require(path)
}
You could change the module to return a function, like this:
// some/module.js
module.exports = function(mainModule) {
var main = mainModule;
return {
someMethod: function() {
main.doSomethingElse();
}
}
}
Then require it passing the main object:
function Main(arg) {
var main = {
auth: auth,
other: stuff,
};
main.module = require('/some/module')(main);
return main;
}
I would like to know how can I import an external library to nodejs.
For example I would like to have phanotmjs library (I know that arelady exist an npm to get phantomjs, but is only an example).
I think that a way was to get the source file of library and include it into a module like that:
module.exports = function (name, cb) {
//source code of library
});
But I think it is a wrong way of doing it.
How can I include an external library to nodejs project to use it inside the project with its functionality?
Thanks
Without exporting, a no elegant way is to copy past the entire library, in the bottom of your node file. nasty you may already thought about it. there is also a bad thing about that. you will not be able to reuse it in all different files.
The other way is to export the files along your workflow every time you need a function. And i think this is ok.
Otherwise to answer that, you can write the export this way:
module.exports = {
removeElementFromArray_Mutate,
hasClass,
hasClass_ONEtest,
removeClassFromAll,
addClass,
removeClass
};
you can do that with node. all of those are normal function declared this way:
function removeClassFromAll(DOMobject, classes){
for(let i = 0; i < DOMobject.length; i++){
removeClass(DOMobject[i], classes);
}
}
function hasClass_ONEtest(DOMElement, classe) {
let allClasses = DOMElement.className.split(/\s+/);
for(let i = 0; i < allClasses.length; i++){
if(allClasses[i].trim() === classe){
return true;
}
}
return false;
}
function hasClass(DOMElement, classes) {
if (typeof classes === 'string') {
return hasClass_ONEtest(DOMElement, classes);
} else { // multiple classes as array
for (let i = 0; i < classes.length; i++) {
if (!hasClass_ONEtest(DOMElement, classes[i])) {
return false;
}
}
return true;
}
}
this way you can write a quick script that parse all the file, and take out the definitions of the functions, if you can't do it manually. You can use regex, to speed up that. you need two patterns. the first for function name( and the second for name = function(. Hope that was helpful!
the question was more about if there is a way included with nodejs. There is none at the moment. it may be in the future. You may also see this How do I include a JavaScript file in another JavaScript file?. It may not help though.
When one requires a module on nodejs, the content of module.exports is returned. So, one can return a function (as you do on your example) or an object, as in
in module.js:
module.exports={
func:function(){ return true; },
val:10,
...
}
So that, in the requiring file, you can:
var m=require('module');
assert(m.func()===true);
assert(10===m.val);
This is explained in the nodejs documentation under Modules
So if you have an external JS library that exposes three functions: a, b, and c, you might wrap them as:
module.exports={
exportedA:lib.a,
exportedB:lib.b,
exportedC:lib.c
};
lib.a=function(){ ... };
lib.b=function(){ ... };
lib.c=function(){ ... };
i have a question regarding defining objects in modules.
lets say i have a module:
/*---obj----*/
function A (param){
this.parm=param;
function func(){
//do somthing
}
}
exports.func=func;
/*---file.js----*/
obj=require('obj');
function fileFunc(A){
A.func();//with out this line it works fine
A.param=2;
}
}
for some reason it does not recognize the function in the object A. it recognizes the object A and its different vars, but when it comes to executing the function it gives the msg:
TypeError: Object # has no method 'func'
i tried also to export the function in A by:
exports.A.func=A.func
or
exports.func=func
neither works..
does someone have a clue?
thanx
matti
The function you defined inside of A is local only to that function. What you want is
function A(param) {
this.param = param;
}
A.func = function() {
// do something
};
But if you are treating A as a constructor then you'll want to put that function in A's prototype
A.prototype.func = function() {
// do something
};