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Calling a JavaScript function in another js file

 原文  2014-09-21 19:19:56  5   17    javascript/ html

Question

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");
}

17 answers

solution1
 197 ACCPTED  2014-09-21 19:26:43

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>

solution2
 27  2015-01-19 06:57:04

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();
});

Hope This Helps... Happy Coding.

solution3
 26  2014-09-21 19:22:23

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." );
});

solution4
 20  2019-09-29 04:43:00

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.

solution5
 7  2018-09-17 14:54:10

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

输出。按钮 + 结果

Try this CodePen snippet: link .

solution6
 5  2018-12-21 21:03:20

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.

solution7
 4  2019-10-06 13:48:22

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>

solution8
 3  2016-11-02 14:46:28

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.

solution9
 3  2017-10-23 02:31:08

first.js

function first() { alert("first"); }

Second.js

var imported = document.createElement("script");
imported.src = "other js/first.js";  //saved in "other js" folder
document.getElementsByTagName("head")[0].appendChild(imported);


function second() { alert("Second");}

index.html

 <HTML>
    <HEAD>
       <SCRIPT SRC="second.js"></SCRIPT>
    </HEAD>
    <BODY>
       <a href="javascript:second()">method in second js</a><br/>
       <a href="javascript:first()">method in firstjs ("included" by the first)</a>
    </BODY>
</HTML>

solution10
 2  2018-03-14 10:40:54

window.onload = function(){
    document.getElementById("btn").onclick = function(){
        fn1();
    }
   // this should work, It calls when all js files loaded, No matter what position you have written
});

solution11
 2  2020-05-11 21:48:51

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

hope this will help somebody, happy coding !!!

solution12
 1  2019-09-28 22:18:02

This is actually coming very late, but I thought I should share,

in index.html

<script type="text/javascript" src="1.js"></script>
<script type="text/javascript" src="2.js"></script>

in 1.js

fn1 = function() {
    alert("external fn clicked");
}

in 2.js

fn1()

solution13
 0  2020-10-20 17:12:14

My idea is let two JavaScript call function through DOM.

The way to do it is simple ... We just need to define hidden js_ipc html tag. After the callee register click from the hidden js_ipc tag, then The caller can dispatch the click event to trigger callee. And the argument is save in the event that you want to pass.

When we need to use above way ?

Sometime, the two javascript code is very complicated to integrate and so many async code there. And different code use different framework but you still need to have a simple way to integrate them together.

So, in that case, it is not easy to do it.

In my project's implementation, I meet this case and it is very complicated to integrate. And finally I found out that we can let two javascript call each other through DOM.

I demonstrate this way in this git code. you can get it through this way. (Or read it from https://github.com/milochen0418/javascript-ipc-demo ) 

git clone https://github.com/milochen0418/javascript-ipc-demo
cd javascript-ipc-demo
git checkout 5f75d44530b4145ca2b06105c6aac28b764f066e

Anywhere, Here, I try to explain by the following simple case. I hope that this way can help you to integrate two different javascript code easier than before there is no any JavaScript library to support communication between two javascript file that made by different team.

<html>
<head>
    <link rel="stylesheet" type="text/css" href="css/style.css" />
</head>
<body>
    <div id="js_ipc" style="display:none;"></div>
    <div id="test_btn" class="btn">
        <a><p>click to test</p></a>
    </div>    
</body>
<script src="js/callee.js"></script>
<script src="js/caller.js"></script>
</html>

And the code css/style.css

.btn {
    background-color:grey;
    cursor:pointer;
    display:inline-block;
}

js/caller.js 

function caller_add_of_ipc(num1, num2) {
    var e = new Event("click");
    e.arguments = arguments;
    document.getElementById("js_ipc").dispatchEvent(e);
}
document.getElementById("test_btn").addEventListener('click', function(e) {
    console.log("click to invoke caller of IPC");
    caller_add_of_ipc(33, 22);      
});

js/callee.js 

document.getElementById("js_ipc").addEventListener('click', (e)=>{
    callee_add_of_ipc(e.arguments);
});    
function callee_add_of_ipc(arguments) {
    let num1 = arguments[0];
    let num2 = arguments[1];
    console.log("This is callee of IPC -- inner-communication process");
    console.log( "num1 + num2 = " + (num1 + num2));
}

solution14
 0  2020-12-14 12:47:23

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");
}

solution15
 0  2021-05-28 06:37:26

better late than never

(function (window) {const helper = { fetchApi: function () { return "oke"}
   if (typeof define === 'function' && define.amd) {
    define(function () { return helper; });
   }
   else if (typeof module === 'object' && module.exports) {
    module.exports = helper;
  }
  else {
    window.helper = helper;
  }
}(window))

index html <script src="helper.js"></script> <script src="test.js"></script>

in test.js file helper.fetchApi()

solution16
 -1  2019-04-03 14:00:11

I have had same problem. I have had defined functions inside jquery document ready function.

$(document).ready(function() {
   function xyz()
   {
       //some code
   }
});

And this function xyz() I have called in another file. This doesn't working :) You have to defined function above document ready .

solution17
 -1  2019-06-28 07:27:36

// module.js
export function hello() {
  return "Hello";
}

// main.js
import {hello} from 'module'; // or './module'
let val = hello(); // val is "Hello";

reference from https://hype.codes/how-include-js-file-another-js-file

solution18
 -1  2022-12-08 20:14:30

TLDR: Load Global Function Files first, Then Load Event Handlers

Whenever you are accessing an element within a JS file or <script> block, it is essential to check to make sure that element exists, ie, jQuery's $(document).ready() or plain JS's document.addEventListener('DOMContentLoaded', function(event)... .

However, the accepted solution does NOT work in the event that you add an event listener for the DOMContentLoaded, which you can easily observe from the comments.

Procedure for Loading Global Function Files First

The solution is as follows:

  • Separate the logic of your JS script files so that each file only contains event listeners or global, independent functions.
  • Load the JS script files with the global, independent functions first.
  • Load the JS script files with event listeners second. Unlike the other previous files, make sure to wrap your code in document.addEventListener('DOMContentLoaded', function(event) {...}) . or document.Ready() .

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