How to Convert a String into a Function Call in JavaScript Without Using `eval`?

Converting a String into a Function Call in JavaScript

Question

You have a string representing a function call, such as:

settings.functionName + '(' + t.parentNode.id + ')'

You want to convert this string into an actual function call, but without using eval.

Solution

Instead of using eval, you can use the following code:

var fn = window[settings.functionName];
if(typeof fn === 'function') {
    fn(t.parentNode.id);
}

This code:

1. Obtains a reference to the function by accessing the global window object and using the settings.functionName property as the key.
2. Checks if the obtained value is a function.
3. If it is a function, calls it with the desired argument.

Example

Consider the following settings object:

/* Somewhere: */
window.settings = {
  /* [..] Other settings */
  functionName: 'clickedOnItem'
  /* , [..] More settings */
};

Later in the code, the following function is defined:

function clickedOnItem (nodeId) {
  /* Some cool event handling code here */
}

Now, you can use the code presented in the solution to make a function call:

/* Even later */
var fn = window[settings.functionName]; 
if(typeof fn === 'function') {
    fn(t.parentNode.id);
}

This will result in the clickedOnItem function being called with the t.parentNode.id as the argument.

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