JS Authoritative Guide Note 1

There are two types of 1.JavaScript data: Primitive Type and object type. The original type also includes numbers, strings, and Booleans, as well as null and undefined, which are a collection of properties, and each property has its own name/value pairs, common object types are functions, arrays (array), dates ( Date), Regular (REGEXP), and Errors (error).

1.1 Data types can also be divided into mutable types and immutable types. Objects and arrays are mutable types , Numbers, Boolean values, and null and undefined are immutable types .

The 2.JAVASCRIPT interpreter has its own memory management mechanism that automates the garbage collection of memory (garbage collection).

3.JavaScript represents numbers in a 64-bit floating-point format defined by the IEEE 754 standard. The integer range that can be representedis -2--253, which contains the boundary value. But in the actual operation is a 32-bit integer.

4. Variable comparisons of primitive types are comparisons of values, whereas objects are compared by reference (because objects are reference types and object values are references).

5.JavaScript is a weakly typed scripting language that converts the type itself as needed when needed. You can also do display type conversions when necessary, such as number (' 3 '), String (false), Boolean ([]), Object (3). (See Rhino P50)

See the Rhino P53 for the conversion steps of the thought string in 6.JavaScript.

Look at these for the time being, and pause for a moment.

JS Authoritative Guide Note 1