Can I access variables from another file?

Question

Is it possible to use a variable in a file called first.js inside another file called second.js?

first.js contains a variable called colorcodes.

Answer 1

As Fermin said, a variable in the global scope should be accessible to all scripts loaded after it is declared. You could also use a property of window or (in the global scope) this to get the same effect.

// first.js
var colorCodes = {
  back  : "#fff",
  front : "#888",
  side  : "#369"
};

... in another file ...

// second.js
alert(colorCodes.back); // alerts `#fff`

... in your html file ...

<script type="text/javascript" src="first.js"></script> 
<script type="text/javascript" src="second.js"></script> 

Answer 2

You can export the variable from first file using export.

//first.js
const colorCode = {
    black: "#000",
    white: "#fff"
};
export { colorCode };

Then, import the variable in second file using import.

//second.js
import { colorCode } from './first.js'

export - MDN

Answer 3

Using Node.js you can export the variable via module.

//first.js
const colorCode = {
    black: "#000",
    white: "#fff"
};
module.exports = { colorCode };

Then, import the module/variable in second file using require.

//second.js
const { colorCode } = require('./first.js')

You can use the import and export aproach from ES6 using Webpack/Babel, but in Node.js you need to enable a flag, and uses the .mjs extension.

Answer 4

This should work - define a global variable in firstfile and access it from secondfile:

<script src="/firstfile.js"></script>
<script src="/secondfile.js"></script>

firstfile.js:

var colors = {
   text:'#000000',
   background:'#aaaaaa',
   something_else:'blue'
};

secondfile.js:

do_something_with(colors.background);

Note that the order in which you load the script files is significant for some browsers (IE6 for sure, maybe others)

Answer 5

I did like the answer above said, but it didn't work for me at first because I was declaring these variables inside jQuery $( document ).ready().

So make sure you declare your variables inside the <script> tag not somewhere else.

Answer 6

I came across amplify.js. It's really simple to use. To store a value, let's call it "myValue", you do:

amplify.store("myKey", "myValue")

And to access it, you do

amplify.store("myKey")

Answer 7

If you store your colorcodes in a global variable you should be able to access it from either javascript file.

Answer 8

I may be doing this a little differently. I'm not sure why I use this syntax, copied it from some book a long time ago. But each of my js files defines a variable. The first file, for no reason at all, is called R:

    var R = 
    { 
        somevar: 0,
        othervar: -1,

        init: function() {
          ...
        } // end init function

        somefunction: function(somearg) {
          ...
        }  // end somefunction

        ...

    }; // end variable R definition


    $( window ).load(function() {
       R.init();
    })

And then if I have a big piece of code that I want to segregate, I put it in a separate file and a different variable name, but I can still reference the R variables and functions. I called the new one TD for no good reason at all:

    var TD = 
    { 
        xvar: 0,
        yvar: -1,

        init: function() {
           ...
        } // end init function

        sepfunction: function() {
           ...
           R.somefunction(xvar);
           ...
        }  // end somefunction

        ...

    }; // end variable TD definition


    $( window ).load(function() {
       TD.init();
    })

You can see that where in the TD 'sepfunction' I call the R.somefunction. I realize this doesn't give any runtime efficiencies because both scripts to need to load, but it does help me keep my code organized.