aoberoi/enumerable_props.md

## enumerable_props.md

      
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              enumerable_props.md
            
          
    Cheatsheet for JavaScript objects as key-value pairs (object literals)

In many JavaScript programs, plain objects are used as a hash map, a dictionary, or as a simple
set of key-value pairs. JavaScript properties can be a little tricky, so this cheatsheet maps out
options for accessing those enumerable properties. Non-enumerable properties are usually not
interesting in this usage (this includes methods, constructor, etc).


Own Properties
Own & Prototype Properties


Exists?
x.propertyIsEnumerable(name)
Requires walking up the prototype chain


As a collection
Object.keys(x) (or Object.entries(x) if working with values too)
Requires walking up the prototype chain


Iterate
Object.keys(x).forEach() (or Object.entries(x).forEach() if working with values too)^*
for (let k in x) { /* ... */ }


^* for...of is better for iterating over true "collection" types, such as Array, String, Set, Map, etc.
	Own Properties	Own & Prototype Properties
Exists?	`x.propertyIsEnumerable(name)`	Requires walking up the prototype chain
As a collection	`Object.keys(x)` (or `Object.entries(x)` if working with values too)	Requires walking up the prototype chain
Iterate	`Object.keys(x).forEach()` (or `Object.entries(x).forEach()` if working with values too)^*	`for (let k in x) { /* ... */ }`