freeCodeCamp/guide/english/certifications/javascript-algorithms-and-data-structures/es6/write-higher-order-arrow-functions/index.md

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Write Higher Order Arrow Functions

Remember to use Read-Search-Ask if you get stuck. Try to pair program and write your own code

Problem explanation:

We need to compute and square values from the realNumberArray and store them in the variable squaredIntegers using the map(), filter(), and/or reduce() functions.

Hint: 1

• You will need to filter() the realNumberArray for positive integers (decimals are not integers).

try to solve the problem now

Hint: 2

• You will need to map() the values from your filter() function to the variable squaredIntegers.

try to solve the problem now

Hint: 3

• Remember the magic of chaining functions.

try to solve the problem now

Spoiler alert!

Solution ahead!

Code solution:

    const squareList = (arr) => {
      "use strict";
      const squaredIntegers = arr.filter((num) => num > 0 && num % parseInt(num) === 0).map((num) => Math.pow(num, 2));
      return squaredIntegers;
    };

    // test your code
    const squaredIntegers = squareList(realNumberArray);
    console.log(squaredIntegers);

• Run code at codepen.io

Code explanation:

Uses the operator filter() and map() functions to square all positive integers in a given array.

Alternative code solution:

  // change code below this line
  const squaredIntegers = arr.filter((param) => Number.isInteger(param) && param >= 0).map(x => x * x);
  // change code above this line

• Run code at repl.it

Code explanation

This does basically the same but uses the isInteger() method to check the numbers.

Resources

• "Array.prototype.map()" - MDN JavaScript reference
• "Array.prototype.filter()" - MDN JavaScript reference
• "Array.prototype.reduce()" - MDN JavaScript reference
• "Number.isInteger()" - MDN JavaScript reference
• "Math.pow()" - MDN JavaScript reference