Dec 31, 2019

The fastest way to look for object properties

I manage a library called onkey-event-manager that helps users map functions to keyboard actions. Part of the library is a validation step that looks for properties on an object.

To make this step as performant as possible, I wanted to know what the fastest method for checking an object for a given property.

Contenders

Object.hasOwnProperty()

This is the built-in method for checking an object for properties. The only question is whether this method is more performant than other options.

const obj = {};

console.log(
    obj.hasOwnProperty('test');
    ? 'exists'
    : 'does not'
)
// -> 'does not'

Object[]

By referencing the property on the object directly, you can let JavaScript’s type coercion to force a boolean.

const obj = {};

console.log(
    obj.test
    ? 'exists'
    : 'does not'
)
// -> 'does not'

Note: This method for checking a property will fail if the value at the given property is false/falsey (e.g. const obj = { test: false }). Since I can guarantee that case won’t happen, I can still use it.

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