How do I fix these JSLint errors?

Question

I'm trying to fix some errors according to JSLint and there are some errors I can't get rid of:

line 46 character 13  
Missing 'new'.  
     SortPosts(categories[categoryNumber].textContent);

line 65 character 16  
Unexpected '('.
    if (typeof (Storage) !== "undefined") {

line 65 character 9Unexpected 'typeof'. Use '===' to compare directly with undefined.
    if (typeof (Storage) !== "undefined") {

This is my code:

window.onload = function () {
    "use strict";
    var categories,
        value,
        i,
        j,
        article,
        li,
        postsAvailable = false;
    function removeElementsByClass() {
        var elements = document.getElementsByClassName("forumPost");
        while (elements.length > 0) {
            elements[0].parentNode.removeChild(elements[0]);
        }
    }
    function addRow(input) {
        article = document.createElement('article');
        article.className = 'forumPost';
        article.innerHTML = "<div id='imageDiv'><img src='" + input.avatar + "' alt='Avatar'id='imageHTML'/><div id='personDiv'> " + input.firstName + " " + input.lastName + " (" + input.age + ") </div><div id='workDiv'>" + input.work + " </div></div><div id='headerDiv'>" + input.firstName + " schreef om <div id='dateDiv'>" + input.date + "</div></div></br><div id='postDiv'>" + input.post + "</div></article>";
        document.getElementById('content').appendChild(article);
    }
    function SortPosts(category) {
        if (localStorage.getItem(category) === "") {
            alert("No posts found!");
        } else {
            removeElementsByClass();
            if (category !== "Algemeen") {
                value = JSON.parse(localStorage.getItem(category));
                for (i = 0; i < value.length; ++i) {
                    addRow(value[i]);
                }
            } else {
                for (i = 0; i < localStorage.length; ++i) {
                    if (localStorage.getItem(localStorage.key(i)) !== "") {
                        value = JSON.parse(localStorage.getItem(localStorage.key(i)));
                        for (j = 0; j < value.length; ++j) {
                            addRow(value[j]);
                        }
                    }
                }
            }
        }
    }
    function getPostSorter(categoryNumber) {
        return function () {
            SortPosts(categories[categoryNumber].textContent);
        };
    }
    document.getElementById("newCategoryButton").onclick = function () {
        var input = document.getElementById("newCategoryInput").value;
        if (input !== "") {
            if (localStorage.getItem(input) !== null) {
                alert("Categorie bestaat al!");
            } else {
                li = document.createElement('li');
                li.innerHTML = "<a href='#'>" + input + "</a></li>";
                localStorage.setItem(input, "");
                document.getElementById("categories").appendChild(li);
            }
        } else {
            alert("Uw invoer mag niet leeg zijn!");
        }
        document.getElementById("newCategoryInput").value = "";
    };
    if (typeof (Storage) !== "undefined") {
        for (i = 0; i < localStorage.length; ++i) {
            if (localStorage.getItem(localStorage.key(i)) !== "") {
                postsAvailable = true;
                break;
            }
        }
        if (postsAvailable === false) {
            article = document.createElement('article');
            article.className = 'infobox';
            article.innerHTML = "<header><h2>Geen posts gevonden!</h2></header><section><p>Ga naar het forum toe om een onderwerp toe te voegen</p></section></article>";
            document.getElementById('content').appendChild(article);
        } else {
            for (i = 0; i < localStorage.length; ++i) {
                if (localStorage.getItem(localStorage.key(i)) !== "") {
                    value = JSON.parse(localStorage.getItem(localStorage.key(i)));
                    for (j = 0; j < value.length; ++j) {
                        addRow(value[j]);
                    }
                }
            }
        }
        for (i = 0; i < localStorage.length; ++i) {
            li = document.createElement('li');
            li.className = "category";
            li.innerHTML = "<a href='#'>" + localStorage.key(i) + "</a></li>";
            document.getElementById("categories").appendChild(li);
        }
        categories = document.getElementsByClassName("category");
        for (i = 0; i < categories.length; ++i) {
            categories[i].addEventListener("click", getPostSorter(i));
        }
    } else {
        alert("Uw browser ondersteunt geen localStorage. Gebruik alstublieft een nieuwere browser zoals Google Chrome, Mozilla Firefox of > Internet Explorer 7");
    }
};

Could anyone tell me why these are wrong and what I should do to fix them? I've googled some more information but I wasn't able to actually find anything helpful. I've tried adding "new" to the SortPosts but then it gave me the message Do not use 'new' for side effects.

Answer 1

To fix these issues, change line 45 to this:

        newSortPosts(categories[categoryNumber].textContent);

Renaming SortPosts to newSortPosts in your code.

On line 65 you don't need to compare the typeof, rather you can just see if Storage is undefined:

if (Storage !== undefined) {

Just a note you when using typeof, you don't need parentheses as typeof is an operator: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/typeof

Answer 2

Missing 'new'.
SortPosts(categories[categoryNumber].textContent);

Functions with names starting with capital letters are, by convention, constructor functions. Yours is not. Rename the function to sortPosts.

Unexpected '('.
if (typeof (Storage) !== "undefined") {

typeof is an operator, not a function.

Use typeof Storage not typeof (Storage).

line 65 character 9Unexpected 'typeof'. Use '===' to compare directly with undefined.

Don't use typeof. Use Storage !== undefined.

NB: JSLint is a very opinionated linter. It is possible for undefined to be overridden. I prefer the typeof approach.