Javascript Week 4 Code From Class

converting-to-arrow-functions.js

/*************** Is Yes No ***************/

// The original function
function isYesNo(answer) {
    return answer.toLowerCase() === "yes" || answer.toLowerCase() === "no";
}

// Converted into a one line arrow function
const isYesNo = (answer) => answer.toLowerCase() === "yes" || answer.toLowerCase() === "no";


/*************** Get Animal By Name ***************/

// The original function
function getAnimalByName(name, animals) {
    return animals.find(function(animal) {
        return animal.name.toLowerCase() === name.toLowerCase();
    });
}

// Converted into an arrow function on multiple lines
const getAnimalByName = (name, animals) => {
    const doesNameMatch = (a) => a.name.toLowerCase() === name.toLowerCase()
    animals.find( doesNameMatch );
}

// Advanced: Converted into a one line arrow function
const getAnimalByName = (name, animals) => animals.find( (a) => a.name.toLowerCase() === name.toLowerCase() );

my-array-methods.js

// My version of what's happening inside the array .find() method
// The actual find method does not have the array parameter!
const myFind = (array, callback) => {
    for(let item of array) {
        const isCorrectOne = callback(item);
        if(isCorrectOne) {
            return item;
        }
    }
}

// My version of what's happening inside the array .map() method
// The actual map method does not have the array parameter!
const myMap = (array, callback) => {
    const newArray = [];
    for(let item of array) {
        const newItem = callback(item);
        newArray.push(newItem);
    }
    return newArray;
}

// My version of what's happening inside the array .filter() method
// The actual filter method does not have the array parameter!
const myFilter = (array, callback) => {
    const filteredArray = [];
    for(let item of array) {
        const shouldKeep = callback(item);
        if(shouldKeep) {
            filteredArray.push(item);
        }
    }
    return filteredArray;
}

// My version of what's happening inside the array .reduce() method
// The actual reduce method does not have the array parameter!
const myReduce = (array, callback, initialValue) => {
    let accumulator = initialValue;
    for(let item of array) {
        accumulator = callback(accumulator, item);
    }
    return accumulator;
}

reduce-highest-number.js

// Using reduce to get the highest number in an array
let numbers = [12, 3, 15, 7, 20, 3];

const highest = numbers.reduce( (currentHighest, number) => {
    if(number > currentHighest) {
        return number;
    }
    return currentHighest;
}, 0);

/* PURELY FOR TEACHING PURPOSES */
/* This is what it would look like if we used my version of reduce instead */
/* There's no reason to ever use my version */
// const highest = myReduce(numbers, (currentHighest, number) => {
//     if(number > currentHighest) {
//         return number;
//     }
//     return currentHighest;
// }, 0);

alert(highest);