Javascript Object Dynamic Key

Accessing a sub-object of a dynamic value yields another dynamic value, even if the sub-object has a different underlying type. Use the gettype function to discover the actual underlying type of the value, and any of the cast function listed below to cast it to the actual type. JavaScript provides a bunch of good ways to access object properties. The dot property accessor syntax object.property works nicely when you know the variable ahead of time. When the property name is dynamic or is not a valid identifier, a better alternative is square brackets property accessor: object propertyName. ES6 defines ‘ComputedPropertyName’ as part of the grammar for object literals, which helps use a variable for a key. Object keys can be dynamically assigned in ES6 by placing an expression in square brackets.

  1. Maps are an improved version of plain objects. You can get the size of a map (for a plain object you have to do it manually) and use as key any object type (plain object uses as key a string primitive type). Let’s see what return.values and.entries map’s methods: //.
  2. Square brackets: jsObj'key' + i = 'example' + 1; In JavaScript, all arrays are objects, but not all objects are arrays. The primary difference (and one that's pretty hard to mimic with straight JavaScript and plain objects) is that array instances maintain the length property so that it reflects one plus the numeric value of the property whose name is numeric and whose value, when converted.

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Objects are dynamic collections of properties, with a “hidden” property to the object’s prototype.

A property has a key and a value.

Property key

The property key is a unique string.

There are two ways to access properties: dot notation and bracket notation. When the dot notation is used, the property key must be a valid identifier.


Accessing a property that doesn’t exist will not throw an error, but will return undefined .


JavaScript treats primitives, objects, and functions like objects.

Objects are dynamic in nature and can be used as maps.

Objects inherit from other objects. Constructor functions and class are sugar syntax for creating objects that inherit from other prototype objects.

Object.create() can be used for single inheritance and Object.assign() for multiple inheritance.

Factory functions can build encapsulated objects.

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Discover Functional JavaScript was named one of thebest new Functional Programming books by BookAuthority!

Javascript object dynamic key value

For more on applying functional programming techniques in React take a look atFunctional React.

Javascript object dynamic key value

Javascript Access Object Dynamic Key

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