What are the results of typeof in JavaScript?
Table of Contents
Introduction
In JavaScript, the typeof operator is used to determine the type of a given operand. It returns a string that represents the data type of the evaluated expression. Understanding the possible results of typeof is essential for type-checking and debugging in JavaScript development.
Possible Results of typeof in JavaScript
1. "string"
If the operand is a string, typeof will return "string".
2. "number"
If the operand is a number, whether an integer or a floating-point value, typeof will return "number".
3. "boolean"
For boolean values (true or false), typeof returns "boolean".
4. "undefined"
If the operand is not defined or has no value, typeof returns "undefined".
5. "object"
Objects, arrays, and even null return "object". However, note that this is a special case where null also returns "object", which can sometimes be confusing.
6. "function"
When the operand is a function, typeof returns "function".
7. "symbol"
For symbols, which are used to create unique identifiers, typeof returns "symbol".
8. "bigint"
For large integer values beyond the safe integer limit, typeof returns "bigint".
Practical Usage of typeof
Type Checking with typeof
When writing JavaScript, you can use typeof to check the type of a variable before performing operations on it. This helps prevent unexpected errors.
Checking for Undefined Variables
You can use typeof to safely check if a variable has been declared or defined.
Conclusion
The typeof operator in JavaScript returns a string indicating the type of the operand, which includes results such as "string", "number", "boolean", "undefined", "object", "function", "symbol", and "bigint". Understanding these results helps with type-checking, debugging, and writing efficient JavaScript code.