Determine whether the input is empty and obtain the JS code of the input type_javascript skills

Use typeof algorithm

The operand of typeof is undefined, and the returned value is "undefined".

The following defines x as the operand:

There are five situations;

The operand is a number, typeof(x) returns "number";

String typeof(x) returns "string";

Boolean value typeof(x) returns "boolean";

Object, array, null: typeof(x) returns "object";

The function typeof(x) returns "function".

For example:

Copy code The code is as follows: