Disallow Function Constructor (no-new-func)

It’s possible to create functions in JavaScript using the Function constructor, such as:

var x = new Function("a", "b", "return a + b");

This is considered by many to be a bad practice due to the difficult in debugging and reading these types of functions.

Rule Details

This error is raised to highlight the use of a bad practice. By passing a string to the Function constructor, you are requiring the engine to parse that string much in the way it has to when you call the eval function.

var x = new Function("a", "b", "return a + b");
var x = Function("a", "b", "return a + b");

The following patterns are considered okay and do not cause warnings:

var x = function (a, b) {
    return a + b;

When Not To Use It

In more advanced cases where you really need to use the Function constructor.

Further Reading


This rule was introduced in ESLint 0.0.7.