CODEWITHSUNDEEP
javascriptnode.js
justZito
justZito

Reputation: 559

Node.JS module.exports for passing parameter between two functions?

I am new to Node.js so this is probably a fundamental question and I am missing something obvious. In the code below, I am trying to set the sql_file name from foo but I keep getting an error on the file not existing because the variable is not working. If I hard code the file name in sql_util.js it works fine.

So how do I pass a parameter or any object from one js file into the function of another?

foo.js

var misc = require('./sql_get');
console.log(misc.sql_file("on.sql"));

sql_util.js

fs = require('fs');
file = 'on.sql'
function sql_file(cb) {
    var fileName = "./SQLs/" + sql_file;
    fs.readFile(fileName, function(err, buffer) {
        if (err) return cb(err);
        return cb(null, buffer.toString());
    });
}
sql_file(function(err, sqlstatement) {
    if (err) throw err;
    console.log('sql statement is: ' + sqlstatement);
});
};
module.exports.x = x;
module.exports.sql_fil = sql_file;

Upvotes: 2

Views: 6808

Answers (2)

Brandon
Brandon

Reputation: 10028

Let's go through this line by line because I see a lot of errors, both syntax and semantic.

foo.js

var misc = require('./sql_get');
console.log(misc.sql_file("on.sql"));

You defined in the function below sql_file to be asynchronous, so it does not return a value, but takes a callback that it passes the result to.

sql_util.js

fs = require('fs');
file = 'on.sql'

You have an unused module-global variable file. Remove this. It's going to cause confusion.

function sql_file(cb) {
    var fileName = "./SQLs/" + sql_file;

sql_file is a function. I can tell because this code lives in a function called sql_file. Therefore, fileName will be "./SQLs/" + the .toString() result of the function, which is the source of the function. I think perhaps you want a parameter?

    fs.readFile(fileName, function(err, buffer) {
        if (err) return cb(err);
        return cb(null, buffer.toString());
    });
}

This seems ok.

sql_file(function(err, sqlstatement) {
    if (err) throw err;
        console.log('sql statement is: ' + sqlstatement);
    });
};

I am not sure what you are trying to do here. Why are you calling the function?

module.exports.x = x;
module.exports.sql_fil = sql_file;

Both of these lines have a problem. There is no symbol defined named x. I am surprised this code runs without throwing an error on that line. Second, you are exporting sql_file as sql_fil, missing the letter e.

The Solution

Since what you asked about is parameter passing and you only have a single function, let's simplify this. You never want to use global variables. If a function needs a particular variable, just pass it as an argument.

foo.js

var misc = require('./sql_get');
misc.sql_file('on.sql', function (err, contents) {
    console.log(contents);
});

sql_get.js (notice the file is renamed)

var fs = require('fs');

function sql_file(sqlFilename, cb) {
    var fileName = "./SQLs/" + sqlFilename;
    fs.readFile(fileName, function(err, buffer) {
        if (err) return cb(err);
        return cb(null, buffer.toString());
    });
}

module.exports.sql_file = sql_file;

Upvotes: 3

Mukesh Soni
Mukesh Soni

Reputation: 6668

A few problems:

  1. You're requiring sql_get but naming the other file sql_util

    var misc = require('./sql_util');

  2. You're exporting module.exports.sql_fil = sql_file; (see the missing e). You probably mean;

    module.exports.sql_file = sql_file;

  3. While calling sql_file, you are passing a string but expecting a cb in the function itself - 

    misc.sql_file("on.sql", function(err, fileContent) {
    if(err) return console.log(err);
    console.log('File content: ', fileContent);
});

function sql_file(sqlFileName, cb) {
    var fileName = "./SQLs/" + sqlFileName;
    fs.readFile(fileName, function(err, buffer) {
        if (err) return cb(err);
        return cb(null, buffer.toString());
    });
}

And I don't know what you are doing with calling sql_file function in that file itself. Remove that.

Upvotes: 3

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