TypeScript integer parsing with Error Handling

TypeScript Error Handling : Exercise-3 with Solution

Write a TypeScript function that parses an integer from a string. Handle potential exceptions caused by invalid input using try-catch.

Sample Solution:

TypeScript Code:

function parseIntegerFromString(input: string): number | null {
  try {
    // Attempt to parse the integer from the input string
    const parsedInt = parseInt(input, 10);

    // Check if the parsing result is NaN (not a number)
    if (isNaN(parsedInt)) {
      throw new Error("Invalid input: Not a valid integer.");
    }

    return parsedInt;
  } catch (error: any) { // Specify the type of 'error' as 'any' or a more specific type
    // Handle the error and return null to indicate failure
    console.error(`Error: ${error.message}`);
    return null;
  }
}

// Test the function with valid and invalid input
const validInput = "100";
const invalidInput = "TypeScript";

const parsedValid = parseIntegerFromString(validInput);
if (parsedValid !== null) {
  console.log(`Parsed Integer (Valid Input): ${parsedValid}`);
} else {
  console.log("Parsing failed for valid input.");
}

const parsedInvalid = parseIntegerFromString(invalidInput);
if (parsedInvalid !== null) {
  console.log(`Parsed Integer (Invalid Input): ${parsedInvalid}`);
} else {
  console.log("Parsing failed for invalid input.");
}

Explanations:

In the exercise above -

• The "parseIntegerFromString()" function attempts to parse an integer from the input string using parseInt.
• Inside the try block, it checks if the parsing result is NaN (not a number) and throws an error if the input is invalid.
• If an error occurs, the catch block catches the error, displays an error message, and returns null to indicate a parsing failure.
• Finally, we test the function with both valid and invalid input strings and display the parsed integers or failure messages accordingly.

Output:

"Parsed Integer (Valid Input): 100" 
"Error: Invalid input: Not a valid integer." 
"Parsing failed for invalid input."

TypeScript Editor:

See the Pen TypeScript by w3resource (@w3resource) on CodePen.

Previous: TypeScript custom Error Handling example.
Next: TypeScript file Handling with Error Catching.