I wanted to call a function defined in a first.js file in second.js file. Both files are defined in an HTML file like:
<script type="text/javascript" src="first.js"></script>
<script type="text/javascript" src="second.js"></script>
I want to call fn1() defined in first.js in second.js. From my searches answers were if first.js is defined first it is possible, but from my tests I haven't found any way to do that.
Here is my code:
second.js
document.getElementById("btn").onclick = function() {
fn1();
}
first.js
function fn1() {
alert("external fn clicked");
}
16 Answers
A function cannot be called unless it was defined in the same file or one loaded before the attempt to call it.
A function cannot be called unless it is in the same or greater scope then the one trying to call it.
You declare function fn1 in first.js, and then in second you can just have fn1();
1.js:
function fn1 () {
alert();
}
2.js:
fn1();
index.html :
<script type="text/javascript" src="1.js"></script>
<script type="text/javascript" src="2.js"></script>
You could consider using the es6 import export syntax. In file 1;
export function f1() {...}
And then in file 2;
import { f1 } from "./file1.js";
f1();
Please note that this only works if you're using <script src="./file2.js" type="module">
You will not need two script tags if you do it this way. You simply need the main script, and you can import all your other stuff there.
1st JS:
function fn(){
alert("Hello! Uncle Namaste...Chalo Kaaam ki Baat p Aate h...");
}
2nd JS:
$.getscript("url or name of 1st Js File",function(){
fn();
});
You can make the function a global variable in first.js
and have a look at closure and do not put it in document.ready put it outside
you can use ajax too
$.ajax({
url: "url to script",
dataType: "script",
success: success
});
same way you can use jquery getScript
$.getScript( "ajax/test.js" )
.done(function( script, textStatus ) {
console.log( textStatus );
})
.fail(function( jqxhr, settings, exception ) {
$( "div.log" ).text( "Triggered ajaxError handler." );
});
declare function in global scope with window
first.js
window.fn1 = function fn1() {
alert("external fn clicked");
}
second.js
document.getElementById("btn").onclick = function() {
fn1();
}
include like this
<script type="text/javascript" src="first.js"></script>
<script type="text/javascript" src="second.js"></script>
use "var" while creating a function, then you can access that from another file. make sure both files are well connected to your project and can access each other.
file_1.js
var firstLetterUppercase = function(str) {
str = str.toLowerCase().replace(/\b[a-z]/g, function(letter) {
return letter.toUpperCase();
});
return str;
}
accessing this function/variable from file_2.js file
firstLetterUppercase("gobinda");
output => Gobinda
It should work like this:
1.js
function fn1() {
document.getElementById("result").innerHTML += "fn1 gets called";
}
2.js
function clickedTheButton() {
fn1();
}
index.html
<html>
<head>
</head>
<body>
<button onclick="clickedTheButton()">Click me</button>
<script type="text/javascript" src="1.js"></script>
<script type="text/javascript" src="2.js"></script>
</body>
</html>
output
Try this CodePen snippet: link .
Please note this only works if the
<script>
tags are in the body and NOT in the head.
So
<head>
...
<script type="text/javascript" src="first.js"></script>
<script type="text/javascript" src="second.js"></script>
</head>
=> unknown function fn1()
Fails and
<body>
...
<script type="text/javascript" src="first.js"></script>
<script type="text/javascript" src="second.js"></script>
</body>
works.
Use cache if your server allows it to improve speed.
var extern =(url)=> { // load extern javascript
let scr = $.extend({}, {
dataType: 'script',
cache: true,
url: url
});
return $.ajax(scr);
}
function ext(file, func) {
extern(file).done(func); // calls a function from an extern javascript file
}
And then use it like this:
ext('somefile.js',()=>
myFunc(args)
);
Optionally, make a prototype of it to have it more flexible. So that you don't have to define the file every time, if you call a function or if you want to fetch code from multiple files.
first.js
function first() { alert("first"); }
