CODEWITHSUNDEEP
javascriptobject
bilal_azam
bilal_azam

Reputation: 4800

Using integer keys with dot notation to access property in javascript objects

Why can't we use integer keys in dot expression to access property values ? 

var obj = {1: 'one', two: '2'}
console.log(obj.1) // error
console.log(obj.two)

Upvotes: 6

Views: 2161

Answers (3)

Tinu Jos K
Tinu Jos K

Reputation: 930

Adding to @Arun P Johny' s answer we can use obj['1'] with quotes or obj[1] without quotes in case of integer. where as accessing obj['two'] will work but obj[two] will throw an error if there is no variable/constant as two.

Upvotes: 0

Arun P Johny
Arun P Johny

Reputation: 388406

In case of dot notation to access a value, the property key must be a valid identifier

In this code, property must be a valid JavaScript identifier, i.e. a sequence of alphanumerical characters, also including the underscore ("_") and dollar sign ("$"), that cannot start with a number. For example, object.$1 is valid, while object.1 is not.

You can use bracket notation in this case

obj['1']

Spec: Property Accessors

Upvotes: 13

Ankit Tanna
Ankit Tanna

Reputation: 1819

It is a JavaScript base princible which says variables cannot start with a number. Over here the property is a variable and hence it cannot start with a number.

You can check more about variable definition rules here

Hope this helps.

Upvotes: -2

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