# Vanilla JavaScript Dynamically Calling a Function

Have you ever had the scenario where you needed to call a function, but based on a variable?

In my most recent use case, I have an area of dynamic modules and loop over them; then, if I find one of these, I want to call the function dynamically.

So how do we go about this?

## Defining our Functions

First, let's start by making our functions.

```js
function customClick(button) {
  button.addEventListener('click', function(event) {
    alert('custom click');
  });
}

function customUppercase(input) {
  input.addEventListener('keyup', function() {
    input.value = input.value.toUpperCase();
  });
}
```

Not very exciting functions but good enough to test with.

For this we are going to use the following `HTML`

```html
<input type="text" data-module="customUppercase" /> <br /><br />
<button type="submit" data-module="customClick">Done</button>
```

## JavaScript Dynamically Calling a Function

Ok, let's start by defining our array of custom objects.

```js
var options = ['Click', 'Uppercase'];
```

We will now loop over these:

```js
for (var i = 0; i < options.length; i++) {
  console.log(options[i]);
}
```

Within the modules we need to get all the types that have the data-module we are passing:

```js
for (var i = 0; i < options.length; i++) {
  var items = document.querySelectorAll('[data-module="custom' + options[i] + '"]');
  for (var j = 0; j < items.length; j++) {
    // Call function
  }
}
```

Now, we need to call the function dynamically!

```js
for (var i = 0; i < options.length; i++) {
  var items = document.querySelectorAll('[data-module="custom' + options[i] + '"]');
  for (var j = 0; j < items.length; j++) {
    this['custom' + options[i]](items[j]);
  }
}
```

That's it! Have a shot at this Codepen.

%[https://codepen.io/rebelchris/pen/LYGgwom]

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