1, string? : There are ""or ""outside the data. Classify the types into strings! ; Any data can be represented, or any type of data can be represented in the form of a string.

2. Numbers? Number (there is no difference between integer and floating-point types: both integers and decimals are numeric types,).

3. Boolean? There are only two expression values: true and false, which are generally used to judge the logic of the program and control the flow of the program.

4.undefined: When a variable is declared as unassigned, the computer defaults to undefined.

5.null？ : You can clear a variable by setting its value to null.

The basic data types of JavaScript are:

1, numeric type: Unlike strongly typed languages such as C and Java, the numeric type of JavaScript includes not only all integer variables, but also all floating-point variables. The numerical values in JavaScript language are all saved in IEEE 754 double-precision floating-point number format.

2. String type: Fuchuan, a substring of JavaScript, must be enclosed in quotation marks. The quotation marks here can be single quotation marks or double quotation marks.