Original ecmascript type

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Ecmascript has five primitive types: undefined, null, Boolean, number, and string.

1. typeof Operator

The typeof operator has a parameter, that is, the variable or value to be checked.

For example:

VaR EMP = "Hello World ";

Alert (typeof EMP); // output "string"

Alert (typeof 100); // output "Number"

---- If the variable is of the undefined type, undefined is returned;

---- If the variable is of the boolean type, the return value is boolean;

---- If the variable is of the number type, return number;

---- If the variable is of the string type, the return value is string;

---- If the variable is of the reference or null type, the object is returned.

Note: The typeof operator returns "object" for the null value, which is actually an error in the initial implementation of JavaScript and is followed by ecmascript. Now null is considered a placeholder for an object, which explains this contradiction, but technically it is still the original value.

2. Number Type

This data type can be a 32-bit integer or a 64-bit floating point number.

What's interesting about floating point literal is that before using it for computation, strings are actually stored.

Extended knowledge points:

① Common division functions

② Common multiplication Functions

Original ecmascript type