根据另一个属性设置嵌套对象属性

Question

I want to calculate how many times characters appear in a text, and then display the totals for each character. My main problem is the first part.

Here is a snapshot of my code so far:

//define text and characters to be searched for
var theArticle = document.getElementById('theText'),
    docFrag = document.createDocumentFragment(),
    theText = theArticle.innerText,
    characters = {
    a: {
        regExp: /a/g,
        matches: [],
        count: 0
    },
    b: {
        regExp: /b/g,
        matches: [],
        count: 0
    },
    c: {
        regExp: /c/g,
        matches: [],
        count: 0
    }

    etc…
}

for (var key in characters) {
    if (characters.hasOwnProperty(key)) {
        var obj = characters.key;
        for (var prop in obj) {
            if (obj.hasOwnProperty(prop)) {
                matches = theText.match(regExp); // pretty sure my problem is here
                count = matches.length; // and here
            }
        }
    }
}

I would like to loop through all the characters to set the value of matches based on regExp and the value of count based on the length of matches .

The top answer to this question is the closest I've come to solving my problem. Access / process (nested) objects, arrays or JSON

Answer 1

There are several changes that should be made to your code:

1. There is no need for the check: if (characters.hasOwnProperty(key)) inside your for in loop.
2. You can't access a variable property with dot notation: var obj = characters.key; should be var obj = characters[key]; .
3. Again, no need for the check: if (obj.hasOwnProperty(prop)) .
4. If you're trying to manipulate the character object properties you need to access the properties on the object, not just by typing the key name.

Correct these things (mainly #2) and it should work as intended.

However, I would completely retool the implementation of your functionality like so:

I would first simply define an array of character strings:

var characters = ['a','b','c','asd'];

Then write a generic function to handle your functionality:

function findCharsInString(array, string) {
    // map a "results" function to each character in the array
    return array.map(function(c) {
        // make a check to ensure we're working with a string that is only one character
        if (typeof c === 'string' && c.length === 1) {
            // create a RegExp from each valid array element
            var matches = string.match(RegExp(c, 'g'));
            // return an anonymous results object for each character
            return {
                matches: matches,
                count: matches.length
            };
        } else { // if there is an invalid element in the array return something
            return 'Invalid array element.';
        }
    });
}

And apply it to your characters array and theText string:

var theText = 'asjdbasccshaskjhsa';
console.log(findCharsInString(characters, theText));

Logs:

[
    {
        matches:
            ["a","a","a","a"],
        count:
            4
    },
    {
        matches:
            ["b"],
        count:
            1
    },
    {
        matches:
            ["c","c"],
        count:
            2
    },
    "Invalid array element."
]