Reducing code duplication when parsing

Question

I prefer to have as little duplicate code as possible within my code base and as such I am constantly looking for ways to reduce it.

I have however become a little stuck on the following case: Say I have a method that parses output from one program into an object to make it readable in another program.

My current approach is to use regex to scan the input to form a new object for output.

This creates a long list of if statements that look more or less the same with slight variations here and there. Is there a meaningful way to reduce the code duplication here or is this something I have to live with?

if ((match = block.match(/bssid=([A-Fa-f0-9:]{17})/))) {
    parsed.bssid = match[1].toLowerCase();
}

if ((match = block.match(/freq=([0-9]+)/))) {
    parsed.frequency = parseInt(match[1], 10);
}

if ((match = block.match(/mode=([^\s]+)/))) {
    parsed.mode = match[1];
}

if ((match = block.match(/key_mgmt=([^\s]+)/))) {
    parsed.key_mgmt = match[1].toLowerCase();
}

Answer 1

I'm guessing you want something like this:

var parseConfig = {
    bssid: {
        expr: /bssid=([A-Fa-f0-9:]{17})/,
        handle: match => match[1].toLowerCase()
    },
    frequency: {
        expr: /freq=([0-9]+)/,
        handle: match => parseInt(match[1], 10)
    },
    mode: {
        expr: /mode=([^\s]+)/,
        handle: match => match[1]
    },
    key_mgmt: {
        expr: /key_mgmt=([^\s]+)/,
        handle: match => match[1].toLowerCase()
    }
};

function parse(block, cfg) {
    var parsed = {};

    Object.keys(cfg).forEach(key => {
        var item = cfg[key],
            match = block.match(item.expr);

        parsed[key] = match ? item.handle(match) : null;
    });

    return parsed;
}