The four types of basic data structures supported by JavaScript are: array lists, maps, records and JSON tables. The following list provides a summary:
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Array lists, such as ["one","two","three"], are special JS objects called 'arrays', but since they are dynamic, they are rather array lists as defined in the Java programming language.
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Maps are also special JS objects, such as {"one":1,"two":2,"three":3}, as discussed below.
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Records, such as {firstName:"Tom",lastName:"Smith"}, are also special JS objects, as discussed below.
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JSON tables are special maps where the values are records representing entities (with a primary key slot), and the keys are the primary keys of these entity records (for an example of such a table, see Storing database tables in JavaScript's Local Storage).
Notice that our distinction between maps, records and JSON tables is a purely conceptual distinction, and not a syntactical one. For a JavaScript engine, both {firstName:"Tom",lastName:"Smith"} and {"one":1,"two":2,"three":3} are just objects. But conceptually, {firstName:"Tom",lastName:"Smith"} is a record because firstName and lastName are intended to denote properties or fields, while {"one":1,"two":2,"three":3} is a map because "one", "two" and "three" are not intended to denote properties/fields, but are just arbitrary string values used as keys in a map.
Making such conceptual distinctions helps to better understand the options offered by JavaScript.
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