The function String.match.length will return an array, so make sure to expect an integer value

Question

The function String.match.length will return an array, so make sure to expect an integer value

I have been working on developing a function that is capable of counting the matches of each letter of the alphabet in a given string. Once I obtain these counts, my goal is to store them in an associative array for easy reference.

However, the issue arises when I use the

string.match(regExpression) || [].length

code snippet, as it returns an array rather than the expected integer value representing the length of the match. My understanding was that the string.prototype.match() method, although returning an array, should still allow me to retrieve the length as a number based on the formal description of the method.

I am curious to know what mistake I might be making in this code implementation?


function countLetters(string) {
    //create array with letters of the alphabet
    var alphabet = "abcdefghijklmnopqrstuvwxyz".split("");
    var counts = []; 

    for (i = 0; i < alphabet.length; i++) {
        var regExpression = new RegExp(alphabet[i], "g"); 
        counts[alphabet[i]] = string.match(regExpression) || [].length;
    }
    return counts; 
}

javascript regex string

Answer 1

Answer №1

After realizing my mistake, I corrected the code that was causing unexpected behavior. The line

string.match(regExpression) || [].length

was not working as expected because I forgot to include parentheses around the match method and logical operator before calling the length method. This caused it to return either the array or the length of an empty array.

In addition, I made a change by using an object instead of an array for counts.

Here is the updated function:

function countLetters(string) {
    // Declare an array with letters of the alphabet
    var alphabet = "abcdefghijklmnopqrstuvwxyz".split("");
    // Declare an object to store our counts
    var counts = {};

    // Iterate through the alphabet array, find matches, and assign the count of matches to the counts object
    for (var i = 0; i < alphabet.length; i++) {
        var regExpression = new RegExp(alphabet[i], "g");
        counts[alphabet[i]] = (string.match(regExpression) || []).length;
    }
    return counts;
}

Answer 2

After realizing my mistake, I corrected the code that was causing unexpected behavior. The line

string.match(regExpression) || [].length

was not working as expected because I forgot to include parentheses around the match method and logical operator before calling the length method. This caused it to return either the array or the length of an empty array.

In addition, I made a change by using an object instead of an array for counts.

Here is the updated function:

function countLetters(string) {
    // Declare an array with letters of the alphabet
    var alphabet = "abcdefghijklmnopqrstuvwxyz".split("");
    // Declare an object to store our counts
    var counts = {};

    // Iterate through the alphabet array, find matches, and assign the count of matches to the counts object
    for (var i = 0; i < alphabet.length; i++) {
        var regExpression = new RegExp(alphabet[i], "g");
        counts[alphabet[i]] = (string.match(regExpression) || []).length;
    }
    return counts;
}

Answer 3

Answer №2

It's not a mistake on your part, but rather a misunderstanding of the expected result. When using string.match correctly, it will return an array as intended.

The purpose of this method is to extract matches from a string that has been compared against a regular expression, and those matches are then stored in an array for further use.

Answer 4

It's not a mistake on your part, but rather a misunderstanding of the expected result. When using string.match correctly, it will return an array as intended.

The purpose of this method is to extract matches from a string that has been compared against a regular expression, and those matches are then stored in an array for further use.

The function String.match.length will return an array, so make sure to expect an integer value

Answer №1

Answer №2

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