freeCodeCamp/curriculum/challenges/english/02-javascript-algorithms-and-data-structures/es6/write-arrow-functions-with-parameters.md

id, title, challengeType, forumTopicId

id	title	challengeType	forumTopicId
587d7b88367417b2b2512b44	Write Arrow Functions with Parameters	1	301223

--description--

Just like a regular function, you can pass arguments into an arrow function.

// doubles input value and returns it
const doubler = (item) => item * 2;
doubler(4); // returns 8

If an arrow function has a single parameter, the parentheses enclosing the parameter may be omitted.

// the same function, without the parameter parentheses
const doubler = item => item * 2;

It is possible to pass more than one argument into an arrow function.

// multiplies the first input value by the second and returns it
const multiplier = (item, multi) => item * multi;
multiplier(4, 2); // returns 8

--instructions--

Rewrite the myConcat function which appends contents of arr2 to arr1 so that the function uses arrow function syntax.

--hints--

You should replace the var keyword.

(getUserInput) => assert(!getUserInput('index').match(/var/g));

myConcat should be a constant variable (by using const).

(getUserInput) => assert(getUserInput('index').match(/const\s+myConcat/g));

myConcat should be an arrow function with two parameters

assert(
  /myConcat=\(\w+,\w+\)=>/.test(code.replace(/\s/g, '')) &&
    typeof myConcat === 'function'
);

myConcat() should return [1, 2, 3, 4, 5].

assert.deepEqual(myConcat([1, 2], [3, 4, 5]), [1, 2, 3, 4, 5]);

function keyword should not be used.

(getUserInput) => assert(!getUserInput('index').match(/function/g));

--seed--

--seed-contents--

var myConcat = function(arr1, arr2) {
  return arr1.concat(arr2);
};

console.log(myConcat([1, 2], [3, 4, 5]));

--solutions--

const myConcat = (arr1, arr2) =>  {
  return arr1.concat(arr2);
};

console.log(myConcat([1, 2], [3, 4, 5]));