JS Hint - don't make functions within a loop

Question

I can not get around JSHint's error message. Here is the loop I am using:

for (i = 0; i < Collection.length; i += 4) {
    data.push({
        items : Collection.slice(i, i + 4).map(function(item) {
            return {
                id: item[0],
                title: item[1],
            };
        })
    });
}

Answer 1

You can just move the function outside the loop and pass a reference to it to map:

function mapCallback(item) {
    return {
        id : item[0],
        title : item[1],
    };
}
for (i = 0; i < Collection.length; i += 4) {
    data.push({
        items: Collection.slice(i, i + 4).map(mapCallback)
    });
}

Alternatively, you can use a JSHint directive to ignore function expressions inside loops. Just put this at the top of the file in question:

/*jshint loopfunc: true */

Answer 2

Declaring a function in a loop is messy, and potentially error prone. Instead, define the function once, and then enter the loop.

var objMaker = function(item) {
    return {
        id : item[0],
        title : item[1],
    };
};

for (i = 0; i < Collection.length; i += 4) {
    data.push({
                  items : Collection.slice(i, i + 4).map(objMaker)
             });
}