可能严格违反-对JavaScript函数使用原型方法

Question

I am getting the following issue with my code. I have a function that will take product data and then return it. We have many options on what we can sort the data on (for example price, name, data, stock levels, etc). Now I pass my data (which is in a JSON format) and depending on the option that is set as an argument I perform the data transform, however I get the following error when I run my code: Possible strict violation.

This is my function to sort the data:

// this is how i call the function, the data argument is the JSON data and formatting options are set in an object literal - this determines the data by name

dataSort(data, {'name':'product name'});

function dataSort(d, obj) {
// we do lots of stuff then later in the function   
for (var key in obj) {
        if(obj.hasOwnProperty(key)){
            if(key === 'name'){
                d = this.getProductByName(d, obj[key]); // This line produces the error
            }
        }
    }
    return d;
}

dataSort.prototype.getProductByName = function(data, val){
    // do stuff the return data
    return data;
};

Now I was alway taught to use the prototype when creating internal methods on functions, why am I getting my error? What am I doing wrong? Should I use a private method or an internal method using this.getProductByName = function(){} Any help will be appreciated.

Answer 1

The correct way to define private helper functions is to use a closure.

var datasort = (function () {
    var getProductByName = function (data, val){
        // do stuff
        return data;
    };

    return function datasort(d, obj) {
        var key;

        // do lots of stuff ...
        return getProductByName(d, obj.name);
    };
}());

getProductByName is now only visible to the inner datasort function (which gets assigned to a variable of the same name).

The effect of the closure is that getProductByName is created only once, instead of with every call of datasort (that would be the case if you moved var getProductByName ... into function datasort ).