Working with Key/Value objects and Arrays

Data:

{
  "apples" : ['Macoun','Empire','Honey Crisp','Albemarle Pippin'],
  "oranges" : ['Naval Orange','Tangelo','Clementine','Valencia Orange']
}

 
 <h1>List of Fruits from Data </h1>
 <div id="fruits"><!-- list goes here -->
 </div>

"use strict";

let fruits = {
    "apples": ['Macoun', 'Empire', 'Honey Crisp', 'Albemarle Pippin'],
    "oranges": ['Naval Orange', 'Tangelo', 'Clementine', 'Valencia Orange']
};
document.addEventListener('DOMContentLoaded',function(){
    buildFruitList();
});

function buildFruitList(){
    let fruitList = document.createElement('ul');
    for (const f in fruits) {
        console.log(f);
        let li = document.createElement('li');
        li.appendChild(document.createTextNode(f));
        if (Array.isArray(fruits[f])) {
            console.log(fruits[f]);
            let itemList = document.createElement('ul');
            for (const item of fruits[f]) {
                let li = document.createElement('li');
                li.appendChild(document.createTextNode(item));
                itemList.appendChild(li);
            }
            li.appendChild(itemList);
        }
        fruitList.appendChild(li);
    }
    document.getElementById('fruits').appendChild(fruitList);
}

JavaScript:

"use strict";

let fruits = {
    "apples": ['Macoun', 'Empire', 'Honey Crisp', 'Albemarle Pippin'],
    "oranges": ['Naval Orange', 'Tangelo', 'Clementine', 'Valencia Orange']
};
document.addEventListener('DOMContentLoaded',function(){
    buildFruitList();
});

function buildFruitList(){
    let fruitList = document.createElement('ul');
    for (const f in fruits) {
        console.log(f);
        let li = document.createElement('li');
        li.appendChild(document.createTextNode(f));
        if (Array.isArray(fruits[f])) {
            console.log(fruits[f]);
            let itemList = document.createElement('ul');
            for (const item of fruits[f]) {
                let li = document.createElement('li');
                li.appendChild(document.createTextNode(item));
                itemList.appendChild(li);
            }
            li.appendChild(itemList);
        }
        fruitList.appendChild(li);
    }
    document.getElementById('fruits').appendChild(fruitList);
}

"use strict"; - what is strict mode?

• Eliminates some JavaScript silent errors by changing them to throw errors.
• Fixes mistakes that make it difficult for JavaScript engines to perform optimizations: strict mode code can sometimes be made to run faster than identical code that's not strict mode.
• Prohibits some syntax likely to be defined in future versions of ECMAScript.