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functional.js
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functional.js
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let numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9]
// Ways of squaring numbers
// Named Function
function square1(array) {
array.forEach(function(element) {
return console.log(element * element)
})
};
// Arrow function
let square2 = array => {
array.forEach(function(element) {
return console.log(element * element)
})
}
//
// USING MAP
//
// Map1 - Anonymous function
numbers.map(function(n) { return n * n });
// Map 2 - Arrow Function
numbers.map((n) => {
return n * n
});
// Map 3 - Arrow function with single argument
numbers.map(n => n * n)
// Apply to slugifying strings
let states = ["Kansas", "Nebraska", "North Dakota", "South Dakota"];
// Slugify a single element
function slugify(element) {
return element.toLowerCase().split(/\s+/).join("-");
};
// Slugify an array - Imperative version
function imperativeUrls(elements) {
let urls = []
elements.forEach(function(element) {
urls.push(slugify(element));
})
return urls
}
// Slugify an array - Functional version
function functionalUrls(elements) {
return elements.map(element => slugify(element))
}
// Append a fully qualified URL to the slugified array
function qualifiedUrl(url, states) {
return states.map(state => url + slugify(state))
}
//
// USING FILTER
//
let states = ["Kansas", "Nebraska", "North Dakota", "South Dakota"];
function imperativeSingles(elements) {
let singles = [];
elements.forEach(function(element) {
if (element.split(/\s+/).length === 1) {
singles.push(element);
}
});
return singles
};
function functionalSingles(elements) {
return elements.filter(element => element.split(/\s+/).length === 1)
}
function functionalSinglesIncludes(elements, includes) {
return elements.filter(element => element.toLowerCase().includes(includes.toLowerCase()))
}
function functionalSinglesRegex(elements) {
return elements.filter(element => element.split(/\s+/).length === 2)
}
//
// USING REDUCE
//
// Imperative sum
function imperativeSum(elements) {
let total = 0
elements.forEach(function(n) {
total += n
console.log(total)
});
return total
}
// Using reduce
numbers.reduce((accumulator, element) => {
accumulator += element
return accumulator
}, 0);
// In one step
numbers.reduce((accumulator, element) => { return accumulator += element }, 0); // The second arg (0) is the starting value of the accumulator (optional in this case)
numbers.reduce((accumulator, element) => { return accumulator *= element });
// Another example
// Imperative
function imperativeLengths(elements) {
let lengths = {};
elements.forEach(function(element) {
lengths[element] = element.length;
});
return lengths
}
function functionalLengths(elements) {
return elements.reduce((lengths, element) => {
lengths[element] = element.length;
return lengths
}, {})
};