Javascript - Variable in function name, possible?

i hope this question is not too simple, but i have no idea :(

How can i start a function with a var in the function name?

For example ...

my functions

function at_26();
function at_21();
function at_99();

start the function

var test_id = 21;	
at_'+test_id+'();   // doesn't work

I hope somebody can help me.

Thanks in advance! Peter

Store your functions in an object instead of making them top level.

var at = {
    at_26: function() { },
    at_21: function() { },
    at_99: function() { }
};

Then you can access them like any other object:

at['at_' + test_id]();

You could also access them directly from the window object…

window['at_' + test_id]();

… and avoid having to store them in an object, but this means playing in the global scope which should be avoided.

You were close.

var test_id = 21
this['at_'+test_id]()

However, what you may want:

at = []
at[21] = function(){ xxx for 21 xxx }
at[test_id]()

You can also try

function at_26(){};
function at_21(){};
function at_99(){};

var test_id = 21;   
eval('at_'+test_id+'()'); 

But use this code if you have very strong reasons for using eval. Using eval in javascript is not a good practice due to its disadvantages such as "using it improperly can open your script to injection attacks."

There is a better way then the window object - which is NOT friendly in firefox - use "self" instead - so in the example posted by Quentin it looks like this:

self['at_' + test_id]();

An example to pass an array of params to those composed functions, .

/* Store function names and match params */
let at = {
    at_26 : (a,b,c) => at_26(a,b,c),
    at_21 : (a,b,c) => at_21(a,b,c),
    at_99 : (a,b,c) => at_99(a,b,c),
    at_om : (a,b,c,d,e) => at_om(a,b,c,d,e)
}

/* Dynamic function router: name + array of Params */
function dynFunc(name, arrayParams){
  return at[name](...arrayParams)
}

/* Usage examples */ 
dynFunc(`at_${99}`, ["track001", 32, true])
dynFunc("at_" + "om", ["track007", [50, false], 7.123, false, "Bye"])


/* In the scope */
function at_99(a,b,c){
  console.log("Hi! " + a,b,c)
  console.log(typeof(a), typeof(b), typeof(c))
}
function at_om(a,b,c,d,e){
  console.log("Hi! " + a,b,c,d,e)
  console.log(typeof(a), typeof(b), typeof(c), typeof(d), typeof(e))
}