[javascript] How do I call a dynamically-named method in Javascript?

I am working on dynamically creating some JavaScript that will be inserted into a web page as it's being constructed.

The JavaScript will be used to populate a listbox based on the selection in another listbox. When the selection of one listbox is changed it will call a method name based on the selected value of the listbox.

For example:

Listbox1 contains:

• Colours
• Shapes

If Colours is selected then it will call a populate_Colours method that populates another listbox.

To clarify my question: How do I make that populate_Colours call in JavaScript?

I wouldn't recommend using the window as some of the other answers suggest. Use this and scope accordingly.

this['yourDynamicFcnName'](arguments);

Another neat trick is calling within different scopes and using it for inheritance. Let's say you had nested the function and want access to the global window object. You could do this:

this['yourDynamicFcnName'].call(window, arguments);

Try with this:

var fn_name = "Colours",
fn = eval("populate_"+fn_name);
fn(args1,argsN);

I would recommend NOT to use global / window / eval for this purpose.
Instead, do it this way:

define all methods as properties of Handler:

var Handler={};

Handler.application_run = function (name) {
console.log(name)
}

Now call it like this

var somefunc = "application_run";
Handler[somefunc]('jerry');

Output: jerry

Case when importing functions from different files

import { func1, func2 } from "../utility";

const Handler= {
  func1,
  func2
};

Handler["func1"]("sic mundus");
Handler["func2"]("creatus est");

A simple function to call a function dynamically with parameters:

this.callFunction = this.call_function = function(name) {
    var args = Array.prototype.slice.call(arguments, 1);
    return window[name].call(this, ...args);
};

function sayHello(name, age) {
    console.log('hello ' + name + ', your\'e age is ' + age);
    return some;
}

console.log(call_function('sayHello', 'john', 30)); // hello john, your'e age is 30

Hi try this,

 var callback_function = new Function(functionName);
 callback_function();

it will handle the parameters itself.

Try These

Call Functions With Dynamic Names, like this:

let dynamic_func_name = 'alert';
(new Function(dynamic_func_name+'()'))()

with parameters:

let dynamic_func_name = 'alert';
let para_1 = 'HAHAHA';
let para_2 = 'ABCD';
(new Function(`${dynamic_func_name}('${para_1}','${para_2}')`))()

Run Dynamic Code:

let some_code = "alert('hahaha');";
(new Function(some_code))()

Within a ServiceWorker or Worker, replace window with self:

self[method_prefix + method_name](arg1, arg2);

Workers have no access to the DOM, therefore window is an invalid reference. The equivalent global scope identifier for this purpose is self.

Here is a working and simple solution for checking existence of a function and triaging that function dynamically by another function;

Trigger function

function runDynmicFunction(functionname){ 

    if (typeof window[functionname] == "function"  ) { //check availability

        window[functionname]("this is from the function it "); //run function and pass a parameter to it
    }
}

and you can now generate the function dynamically maybe using php like this

function runThis_func(my_Parameter){

    alert(my_Parameter +" triggerd");
}

now you can call the function using dynamically generated event

<?php

$name_frm_somware ="runThis_func";

echo "<input type='button' value='Button' onclick='runDynmicFunction(\"".$name_frm_somware."\");'>";

?>

the exact HTML code you need is

<input type="button" value="Button" onclick="runDynmicFunction('runThis_func');">

As Triptych points out, you can call any global scope function by finding it in the host object's contents.

A cleaner method, which pollutes the global namespace much less, is to explicitly put the functions into an array directly like so:

var dyn_functions = [];
dyn_functions['populate_Colours'] = function (arg1, arg2) { 
                // function body
           };
dyn_functions['populate_Shapes'] = function (arg1, arg2) { 
                // function body
           };
// calling one of the functions
var result = dyn_functions['populate_Shapes'](1, 2);
// this works as well due to the similarity between arrays and objects
var result2 = dyn_functions.populate_Shapes(1, 2);

This array could also be a property of some object other than the global host object too meaning that you can effectively create your own namespace as many JS libraries such as jQuery do. This is useful for reducing conflicts if/when you include multiple separate utility libraries in the same page, and (other parts of your design permitting) can make it easier to reuse the code in other pages.

You could also use an object like so, which you might find cleaner:

var dyn_functions = {};
dyn_functions.populate_Colours = function (arg1, arg2) { 
                // function body
           };
dyn_functions['populate_Shapes'] = function (arg1, arg2) { 
                // function body
           };
// calling one of the functions
var result = dyn_functions.populate_Shapes(1, 2);
// this works as well due to the similarity between arrays and objects
var result2 = dyn_functions['populate_Shapes'](1, 2);

Note that with either an array or an object, you can use either method of setting or accessing the functions, and can of course store other objects in there too. You can further reduce the syntax of either method for content that isn't that dynamic by using JS literal notation like so:

var dyn_functions = {
           populate_Colours:function (arg1, arg2) { 
                // function body
           };
         , populate_Shapes:function (arg1, arg2) { 
                // function body
           };
};

Edit: of course for larger blocks of functionality you can expand the above to the very common "module pattern" which is a popular way to encapsulate code features in an organised manner.

you can do it like this:

function MyClass() {
    this.abc = function() {
        alert("abc");
    }
}

var myObject = new MyClass();
myObject["abc"]();