disallow calling global object properties as functions (no-obj-calls)

The "extends": "eslint:recommended" property in a configuration file enables this rule.

ECMAScript provides several global objects that are intended to be used as-is. Some of these objects look as if they could be constructors due their capitalization (such as Math and JSON) but will throw an error if you try to execute them as functions.

The ECMAScript 5 specification makes it clear that both Math and JSON cannot be invoked:

The Math object does not have a [[Call]] internal property; it is not possible to invoke the Math object as a function.

And the ECMAScript 2015 specification makes it clear that Reflect cannot be invoked:

The Reflect object also does not have a [[Call]] internal method; it is not possible to invoke the Reflect object as a function.

Rule Details

This rule disallows calling the Math, JSON and Reflect objects as functions.

Examples of incorrect code for this rule:

/*eslint no-obj-calls: "error"*/

var math = Math();
var json = JSON();
var reflect = Reflect();

Examples of correct code for this rule:

/*eslint no-obj-calls: "error"*/

function area(r) {
    return Math.PI * r * r;
}
var object = JSON.parse("{}");
var value = Reflect.get({ x: 1, y: 2 }, "x");

Further Reading

• The Math Object

Version

This rule was introduced in ESLint 0.0.9.

Resources

• Rule source
• Documentation source