String Type Verification in JavaScript

Determining the data type of a variable is a fundamental task in programming. This challenge focuses on accurately identifying whether a given value is a string in JavaScript, accounting for potential pitfalls and edge cases. A robust solution is crucial for data validation and ensuring correct program behavior.

Problem Description

You are tasked with creating a JavaScript function named isString that takes a single argument, value, and returns true if the value is a string. The function should return false otherwise. The function must correctly handle various input types, including primitive types (number, boolean, null, undefined, symbol) and objects. It should also account for string-like objects (e.g., those with a toString() method) and differentiate them from true strings.

Key Requirements:

• The function must return a boolean value (true or false).
• The function must correctly identify primitive strings.
• The function must correctly identify string-like objects (objects with a toString() method that returns a string).
• The function must return false for all other data types (numbers, booleans, null, undefined, symbols, objects that don't have a useful toString() method).

Expected Behavior:

The function should behave as follows:

• isString("hello") should return true.
• isString(123) should return false.
• isString(true) should return false.
• isString(null) should return false.
• isString(undefined) should return false.
• isString({}) should return false.
• isString(new String("world")) should return true.
• isString(Object.prototype.toString.call(123)) should return false.

Edge Cases to Consider:

• null and undefined are not strings.
• Numbers, booleans, and symbols are not strings.
• Objects that don't have a toString() method or whose toString() method doesn't return a string should not be considered strings.
• The new String() constructor creates a String object, which is a string in JavaScript.

Examples

Example 1:

Input: "hello"
Output: true
Explanation: The input is a primitive string.

Example 2:

Input: 123
Output: false
Explanation: The input is a number, not a string.

Example 3:

Input: new String("world")
Output: true
Explanation: The input is a String object, which is considered a string in JavaScript.

Example 4:

Input: { toString: () => "test" }
Output: true
Explanation: The input is an object with a toString method that returns a string.

Example 5:

Input: { }
Output: false
Explanation: The input is an object without a toString method that returns a string.

Constraints

• The input value can be of any JavaScript data type.
• The function must be implemented using standard JavaScript.
• The function should be efficient and avoid unnecessary operations. While performance isn't a primary concern for this problem, avoid overly complex or inefficient solutions.

Notes

Consider using the typeof operator and the Object.prototype.toString.call() method to accurately determine the type of the input value. Be mindful of the difference between primitive strings and String objects. Think about how to handle objects with custom toString() methods.