How to Determine if a Key in a Map Starts with a Specific String Value

How can I check if a key in a JavaScript Map object starts with a specific string?

const myMap = new Map([['apple', 1], ['banana', 2], ['apricot', 3]]);

In JavaScript, the Map object allows you to store key-value pairs. To check if a key in a Map starts with a specific string, you can iterate through the Map’s keys and use the `startsWith` method of strings.

const myMap = new Map([['apple', 1], ['banana', 2], ['apricot', 3]]);

function keyStartsWith(map, string) {
    for (const key of map.keys()) {
        if (key.startsWith(string)) {
            return true; // The key starts with the specified string.
        }
    }
    return false; // No key found that starts with the specified string.
}

console.log(keyStartsWith(myMap, 'app')); // Output: true
console.log(keyStartsWith(myMap, 'ban')); // Output: true
console.log(keyStartsWith(myMap, 'grape')); // Output: false

Causes

• The key may not exist in the Map, leading to a false result.
• Typographical errors in the string you are checking against.

Solutions

• Utilize the `Map.prototype.has` method to ensure the key exists before checking if it starts with the given string.
• Use the `startsWith` method for string comparison. You may opt for case-insensitive checks if necessary.

Mistake: Forgetting to check if the key exists in the Map before using `startsWith`.

Solution: Always confirm the key's existence using `map.has(key)`.

Mistake: Using a case-sensitive comparison without considering casing variations.

Solution: Normalize the casing by using `toLowerCase()` or `toUpperCase()` before checking.