Iterators Lab

Description

In the iterators lab we will be continuing our exploration of iterators. We have a series of challenges that require you to use the iterators we discussed in class. We will try to use various testing methods to verify that your code is working.

Phase-1

Research the following term and summarize your findings on it two to three sentences:

• higher-order function -->A function is considered 'higher-order' when it's inputs or outputs include another function. Higher- order functions are different from standard functions (first-class functions) because they deal with possibilities over 'actions' rather than just values like in the standard case.

Update this README with a description of each of the following and an example you've created:

• forEach: note =>(SYNTAX > arr.function(callback[, thisarg])

forEach() will execute a given method on 'each' element of an array. EXAMPLE___ var foods = ["burritos", "chips", "candy", "marshmallows]; foods.forEach(function (junk) { console.log("I like " + junk ) }); "I like burritos" "I like chips" "I like candy" "I like marshmallows"

• map: note =>SYNTAX > arr.map(callback[, thisArg])

map() will create a new array using the results of a function that is applied to every element in a given array. EXAMPLE___ var names = ["Michael", "Chris", "Chip", "Sue", "Scott"]; var UpperCased = names.map(function (family) { return family.toUpperCase(); }); console.log(UpperCased);

["MICHAEL", "CHRIS", "CHIP", "SUE", "SCOTT"]

• filter: note =>SYNTAX > arr.filter(callback[, thisArg])

filter() will create a new array and fill it only with elements that remain after a selective function is applied. EXAMPLE___ var desertAnimals = ["snake", "owl", "javelina", "roadrunner", "hummingbird", "rabbit", "coyote", "gilamonster"];

var even = function (animal) { return animal.length % 2 === 0; }; var odd = function (animal) { return animal.length % 2 !== 0;
};

var evenNames = desertAnimals.filter(even); var oddNames = desertAnimals.filter(odd);

console.log(evenNames);["javelina", "roadrunner", "rabbit", "coyote"] console.log(oddNames);["snake", "owl", "hummingbird", "gilamonster"]

• reduce: note =>SYNTAX > arr.reduce(callback[, initialValue])

reduce() will take an array and reduce it to a single value by running a function against an accumulator (a variable that that modifies values in some way other than counting) always from left to right. EXAMPLE ____ var strings = ["anti", "disest", "ablish", "ment", "arian", "ism"];

names.reduce(function (prev, next) { return prev + next; });

antidisestablishmentarianism

• some: note =>SYNTAX > arr.some(callback[, thisArg])

some() will take an array and use a function to test all of the elements in the array to see if some of them return a true value (this is a boolean method). EXAMPLE___ var numbers = [2, 4, 6, 8, 35];

numbers.some(function isEven(numbers) { return numbers % 2 === 0; });

true

• every: note =>SYNTAX arr.every(callback[, thisArg])

every() will apply a given function against all the elements in an array but does not mutate the array itself. var nums= [13, 43, 5, 7, 33, 12, 66]; nums.every(function isSmallEnough(num) { return num <= 15; }); false

Use the notes provided to help guide you explanation.

Phase-2

• Run npm install from the iterators_lab directory.
• Looks at the tests we've written in the test folder. Run the tests with npm test (also from the iterators_lab directory). They should all fail.
• Get all of the tests to pass by writing the necessary code in src/iterators.js.

Phase-3

Refactor the following code using map to make only one call to the map function versus the two below.

var myNumbers = [ -1, 2, -3, 4, -5, 6];

var square = function(num) {
	return num * num;
};

var sqrRoot = function(num) {
	return Math.sqrt(num);
};

return myNumbers.map(square, sqrRoot);



//var sqrNumbers = map(myNumbers, square);
//var absNumbers = map(sqrNumbers, sqrRoot);