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In JavaScript, how to execute next function from an array of functions

I have an array of functions, as in:
funcArray = [func1, func2, func3];
When in a given function, I want to execute the next function in the array. How do I do this? Here is my basic skeleton:
function func1() {
// I get current function caller
var currentFunc = func1.caller;
// I want to execute the next function. Happens to be func2 in the example.
}
I cannot use indexOf function, as one would for an array of strings or numbers.
NOTE: This question appears to be similar to this and the one it refers to. However, it is a different question.
I want to alter the sequence of processing by merely modifying the array. That's the goal. A possibly more efficient approach would be appreciated.
Clarification: Based upon some of the comments:
funcArray is global.
The goal is to implement middleware for a Node.js HTTP module in as simple and efficient a manner as possible without using any third-party modules.

Unless func1 closes over funcArray, you cannot have it reach out and find func2 and execute it, nor should you. Even if func1 does close over funcArray, it would be poor separation of concerns for func1 to reach out and find itself in funcArray and then execute func2.
Instead, have other code that's in charge of running the functions.
If they're synchronous
If the functions complete their work synchronously, then it's simply:
funcArray.forEach(fn => fn());
or
for (const fn of funcArray) {
fn();
}
or if the result of one function should be passed to the next, you can use reduce:
const finalResult = funcArray.reduce((previousResult, fn) => fn(previousResult), undefined);
...where undefined is the value to pass to func1.
If they're asynchronous
If they don't do their work synchronously, you'll need to provide them a way to notify their caller that they've completed their work. Promises are a good, standard way to do that, but you could use simple callbacks instead.
If you make them return promises, for instance, you can use the old promise reduce trick:
funcArray.reduce((p, fn) => {
return p.then(() => {
fn();
});
}, Promise.resolve());
or if the result of one function should be passed to the next:
funcArray.reduce((p, fn) => {
return p.then(fn);
}, Promise.resolve());
You can provide an argument to Promise.resolve to set the value to pass to func1 (without one, it'll receive undefined).

You can bind to the function the index where it is in the array so you can use this index to get and call the next function:
var funcArray = [func1, func2];
var boundFuncArray = funcArray.map((f, i) => f.bind(null, i));
boundFuncArray[0]();
function func1(nextFunctionIndex) {
console.log('func1 called');
// Execute next function:
var nextFunc = boundFuncArray[nextFunctionIndex + 1];
nextFunc && nextFunc();
}
function func2(nextFunctionIndex) {
console.log('func2 called');
// Execute next function:
var nextFunc = boundFuncArray[nextFunctionIndex + 1];
nextFunc && nextFunc();
}
As T.J Crowder stated in the comment below, you can also bind the next function to the current one:
var funcArray = [func1, func2];
var boundFuncArray= funcArray.map((f, i, arr) => f.bind(null, arr[i + 1]));
boundFuncArray[0]();
function func1(nextFunc) {
console.log('func1 called');
// Execute next function:
nextFunc && nextFunc();
}
function func2(nextFunc ) {
console.log('func2 called');
// Execute next function:
nextFunc && nextFunc();
}

You can get the current function's name with arguments.callee.name, loop through the array of functions, and call the next function:
funcArray = [func1, func2, func3];
// Only func1() and func2() will be documented since the others have repeating code
function func1() {
// show the current function name
console.log(arguments.callee.name);
// loop the array of functions
for(var i = 0; i < funcArray.length; ++i)
{
// when the current array item is our current function name and
// another function exists after this then call it and break
if(funcArray[i] === arguments.callee && funcArray[i+1])
{
funcArray[i+1]();
break;
}
}
}
function func2() {
console.log(arguments.callee.name);
// some logic which switches our next function to be func4()
funcArray[2] = func4;
for(var i = 0; i < funcArray.length; ++i)
{
if(funcArray[i] === arguments.callee && funcArray[i+1])
{
funcArray[i+1]();
break;
}
}
}
function func3() {
console.log(arguments.callee.name);
for(var i = 0; i < funcArray.length; ++i)
{
if(funcArray[i] === arguments.callee && funcArray[i+1])
{
funcArray[i+1]();
break;
}
}
}
function func4() {
console.log(arguments.callee.name);
for(var i = 0; i < funcArray.length; ++i)
{
if(funcArray[i] === arguments.callee && funcArray[i+1])
{
funcArray[i+1]();
break;
}
}
}
// call the first function
funcArray[0]();
Output:
func1
func2
func4

I have solved it this way:
// Adding next options to array
function addNext(array) {
array.last = 1
Object.defineProperty(array, 'next', {get:
function() {
if(this.last < this.length) {
this.last++
return this[this.last-1]
} else {
this.last = 1
return () => {}
}
}
});
}
// The functions for array (has to be function and not arrow function)
function first(param) {
console.log('first',param)
return this.next(param)
}
function second(param) {
console.log('second',param)
return this.next(param)
}
function third(param) {
console.log('third',param)
return this.next(param)
}
// The array
let fns = [first,second,third]
// Adding next option to array
addNext(fns)
// Run first function from array
fns[0]('test')

I dont know if your functions require certain parameters but this is the first thing that came to my mind.
var functArray = [
function() {
console.log("function1 executed");
},
function() {
console.log("function2 executed");
},
function() {
console.log("function3 executed");
},
function() {
console.log("function4 executed");
}];
functArray.forEach(function(x){
x();
});

The accepted answer and other comments did help me, but the way I implemented it is as follows:
//The functions are defined as variables.
//They do not get hoisted, so must be defined first.
func1 = function (arg1, arg2) {
//Code to do whatever...
...
//Execute the next function.
//The name of the function is returned by executing nextFunc()
global[nextFunc()](arg1, arg2, arg3);
}
func2 = function (arg1) { //Note different type of args
...
}
//Note that this is an array of strings representing function names.
funcArray = ["func1", "func2", "func3",...]
//Start the execution...
func1(arg1, arg2);
function nextFunc() {
var currentFuncName = nextFunc.caller.name;
var index = funcArray.indexOf(currentFuncName);
if (index < funcArray.length)
return funcArray[index+1];
}
The sequence of functions to be executed is easily managed through the array funcArray. The number or type of arguments is not fixed for each function. Additionally, the functions control if they should stop the chain or continue with the next function.
It is very simple to understand requiring basic Javascript skills. No overheads of using Promises.
"global" gets replaced by "window" for browser. This is a Node.js implementation. The use of function names in the array will, however, break if you minify the JS code. As I am going to use it on the server, I do not expect to minify it.

You can do it in this way with promise.all if your functions to be executed in parallel.
let toBeExecutedList = [];
toBeExecutedList.push(() => this.addTwoNumber(2, 3));
toBeExecutedList.push(()=>this.square(2));
And Then wherever you want to use them, do it like this:
const resultArr = await Promise.all([
toBeExecutedList.map(func => func()),
]);

How can I make a for loop in Javascript that will set timeouts from an array?

Background (You might want to skip this)
I'm working on a web app that animates the articulation of English phonemes, while playing the sound. It's based on the Interactive Sagittal Section by Daniel Currie Hall, and a first attempt can be found here.
For the next version, I want each phoneme to have it's own animation timings, which are defined in an array, which in turn, is included in an object variable.
For the sake of simplicity for this post, I have moved the timing array variable from the object into the function.
Problem
I set up a for loop that I thought would reference the index i and array t to set the milliseconds for each setTimeout.
function animateSam() {
var t = [0, 1000, 2000, 3000, 4000];
var key = "key_0";
for (var i = 0; i < t.length; i++) {
setTimeout(function() {
console.log(i);
key = "key_" + i.toString();
console.log(key);
//do stuff here
}, t[i]);
}
}
animateSam()
However, it seems the milliseconds are set by whatever i happens to be when the function gets to the top of the stack.
Question: Is there a reliable way to set the milliseconds from the array?

The for ends before the setTimeout function has finished, so you have to set the timeout inside a closure:
function animateSam(phoneme) {
var t = [0,1000,2000,3000,4000];
for (var i = 0; i < t.length; i++) {
(function(index) {
setTimeout(function() {
alert (index);
key = "key_" + index.toString();
alert (key);
//do stuff here
}, t[index]);
})(i);
}
}
Here you have the explanation of why is this happening:
https://hackernoon.com/how-to-use-javascript-closures-with-confidence-85cd1f841a6b

The for loop will loop all elements before the first setTimeout is triggered because of its asynchronous nature. By the time your loop runs, i will be equal to 5. Therefore, you get the same output five times.
You could use a method from the Array class, for example .forEach:
This ensures that the function is enclosed.
[0, 1000, 2000, 3000, 4000].forEach((t, i) => {
setTimeout(function() {
console.log(i);
console.log(`key_${i}`);
//do stuff here
}, t)
});
Side note: I would advise you not to use alert while working/debugging as it is honestly quite confusing and annoying to work with. Best is to use a simple console.log.
Some more clarifications on the code:
.forEach takes in as primary argument the callback function to run on each of element. This callback can itself take two arguments (in our previous code t was the current element's value and i the current element's index in the array):
Array.forEach(function(value, index) {
});
But you can use the arrow function syntax, instead of defining the callback with function(e,i) { ... } you define it with: (e,i) => { ... }. That's all! Then the code will look like:
Array.forEach((value,index) => {
});
This syntax is a shorter way of defining your callback. There are some differences though.

I would suggest using a function closure as follows:
function animateSam(phoneme) {
var t = [0,1000,2000,3000,4000];
var handleAnimation = function (idx) {
return function() {
alert(idx);
key = "key_" + idx.toString();
alert(key);
//do stuff here
};
}
for (var i = 0; i < t.length; i++) {
setTimeout(handleAnimation(i), t[i]);
}
}
I this example you wrap the actual function in a wrapper function which captures the variable and passes on the value.

Unary function chainer javascript

My task is to write a higher order function for chaining together a list of unary functions.The first argument is an array, which holds the names of functions to be called.The second param is the value to be used with functions. Here is the code
function square (x) {return x * x;}
function add3 (x) {return x + 3;}
function chainer(a) {
return function (b) {
for(var i = 0; i < a.length; i++) {
return a[i](b)
}
}
}
console.log(chainer([square, add3])(4));
The desired output is 19 but it executes only the first function and prints out 16. I think I would need to compose these functions somehow but can`t wrap my head around it. Would I need to use apply() or call() methods to complete the task? I am new to functional programming.

Your problem is that return a[i](b) does only call the first function and immediately return its result. You will need to put the return after the loop:
for (var i = 0; i < a.length; i++) {
b = a[i](b)
}
return b
Alternatively, this is a great use case for reduce/fold (which you probably have encountered before function composition):
return function(b) {
return a.reduce(function(b, f) { return f(b) }, b)
};
or even
return a.reduce(compose, function id(x) { return x; });

What is the meaning of *[Symbol.iterator] in this context

I found some code online. I've squashed the original code down into this little excerpt, that when ran, will print 1-20 to the console.
var NumbersFromOne = {
*[Symbol.iterator] () {
for (let i = 1;; ++i) yield i;
}
};
var take = function* (numberToTake, iterable) {
let remaining = numberToTake;
for (let value of NumbersFromOne) {
if (remaining-- <= 0) break;
yield value;
}
}
var printToTwenty = take(20, NumbersFromOne)
console.log(...printToTwenty);
Now, I understand that take() is a GeneratorFunction.
When take() is called, it is given an iterator.
The code "...printToTwenty" uses the spread operator to iterate through that function.
I understand that NumbersFromOne is an object.
I've come here looking for an explanation of what this part means:
*[Symbol.iterator] () {}
Declaring generator functions is done like this: function* () {}
So I'm assuming this isn't declaring a generator function.
* also doesn't represent the function name
* also can't be replaced with another operator (/, -, +)
What is the deal with that syntax, and why is the * before [Symbol.iterator]
If placed after, it will not run.
I had considered that *[Symbol.iterator] () is a way to overwrite the existing iterator property, but then wouldn't it say this[Symbol.iterator].
Thanks!

There are a few things that might make this code look complicated:
It uses the object property shorthand notation. What you're seeing here is actually the following:
var NumbersFromOne = {
[Symbol.iterator]: function* () {
for (let i = 1;; ++i) yield i;
}
};
Symbol.iterator creates a custom iterator for your NumbersFromOne object.
So your code basically means that the iterator of NumbersFromOne is defined as a generator. Instead of manually having to define a function which returns a next and other properties:
var NumbersFromOne = {
[Symbol.iterator]: function () {
var i = 1;
return {
next: function() {
return { value: i++, done: false };
}
};
}
};
Returning the generator creates the next function automatically for. This allows you to yield when you need to.
It can then be called as:
const it = NumbersFromOne[Symbol.iterator]();
it.next(); // 1
it.next(); // 2
it.next(); // 3
// ...
Note: Written this way, this iterator never ends! So if you were to call it in a for ... of loop without an end-condition, it would freeze your program.

Passing arguments as an array without .apply()

I am try to find out if there is a way to pass arguments to a javascript function as an array, without using the .apply method. The code would look something like this from a user's perspective:
var args = [1, 2, 3, 4];
doSomething(args);
Note that doSomething() will not always be the same function, so I cannot write it to use an array of arguments. Ideally, this should work for any function, and I guess what I am trying to do is essentially convert an array into an arguments-array-like object.
I was thinking that I may be able to set the functions arguments object like this:
function.arguments = otherArguments;
But I don't know when I would have to do that (wouldn't I have to somehow do it once the function started executing but before it actually did anything with its arguments?)
The reason I am trying to do this is because I am trying to write my own .apply function for learning purposes. Is this possible?

No, there is no way around. One tool for one functionality, and the one of choice is apply.
If you need to write your own function that does not use apply, you would need to use eval:
function apply(fn, thisObj, args) {
var obj = {fn: fn};
var str = "obj.fn(";
for (var i=0; i<args.length; i++)
str += (i?',':'') + "args["+i+"]";
str += ");";
return eval(str);
}

I am not recommending this at all, but if you wanted to be insane, you could probably dynamically generate a curry method for the arity of the function that you are invoking, and then invoke the resulting curry in a loop:
function func(a,b,c,d) {
console.log([a,b,c,d]);
return "Return Value";
}
// Using a static 4 argument curry.
function curry4(f) {
return function(a) {
return function(b) {
return function(c) {
return function(d) {
return f(a,b,c,d);
}
}
}
}
}
var args = [1,2,3,4];
for(var i=0,f=curry4(func);i<func.length;i++) { f = f(args[i]); }
console.log(f); // f is return value of `func`
See here for example that supports up to 12 optional arguments.
But this road probably leads to madness....

Just to mention:
if you use setTimeout you can pass params:
setTimeout( _function_name_, delay, param1,param2,param3...)
this way the params are passed to the function without using apply