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no-new-native-nonconstructor

Disallow new operators with global non-constructor functions

It is a convention in JavaScript that global variables beginning with an uppercase letter typically represent classes that can be instantiated using the new operator, such as new Array and new Map. Confusingly, JavaScript also provides some global variables that begin with an uppercase letter that cannot be called using the new operator and will throw an error if you attempt to do so. These are typically functions that are related to data types and are easy to mistake for classes. Consider the following example:

// throws a TypeError
let foo = new Symbol("foo");

// throws a TypeError
let result = new BigInt(9007199254740991);

Both new Symbol and new BigInt throw a type error because they are functions and not classes. It is easy to make this mistake by assuming the uppercase letters indicate classes.

Rule Details

This rule is aimed at preventing the accidental calling of native JavaScript global functions with the new operator. These functions are:

  • Symbol
  • BigInt

Examples

Examples of incorrect code for this rule:

/*eslint no-new-native-nonconstructor: "error"*/
/*eslint-env es2022*/

var foo = new Symbol('foo');
var bar = new BigInt(9007199254740991);

Examples of correct code for this rule:

/*eslint no-new-native-nonconstructor: "error"*/
/*eslint-env es2022*/

var foo = Symbol('foo');
var bar = BigInt(9007199254740991);

// Ignores shadowed Symbol.
function baz(Symbol) {
const qux = new Symbol("baz");
}
function quux(BigInt) {
const corge = new BigInt(9007199254740991);
}

When Not To Use It

This rule should not be used in ES3/5 environments.

Version

This rule was introduced in ESLint v8.27.0.

Further Reading

Resources