How to use numbers to index arrays in JavaScript

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Many programming languages allow names to be used as indexes on arrays.

An array that uses a name as an index is called an associative array (or hash).

JavaScript does not support indexing arrays with names, only numeric indexes are allowed.

Example

Var person = []

Person [0] = "John"

Person [1] = "Doe"

Person [2] = 46

Var x = person.length; / / person.length returns 3

Var y = person [0]; / / person [0] returns "John"

In JavaScript, objects use the name as the index.

If you use the name as the index, JavaScript redefines the array as a standard object when accessing the array.

After doing this, the methods and properties of the array can no longer be used, otherwise an error will occur:

Example

Var person = []

Person ["firstName"] = "John"

Person ["lastName"] = "Doe"

Person ["age"] = 46

Var x = person.length; / / person.length returns 0

Var y = person [0]; / / person [0] returns undefined

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