CODEWITHSUNDEEP
javascriptarraysfunctionecmascript-6numbers
Rodney Solomon Jr
Rodney Solomon Jr

Reputation: 27

make an array become a function that adds a give value to numbers in the array

So I was given the problem to write a function that will take a given array, add a given number to it and output a new array adding the given number to each element in the array.. so given_array = [1, 2, 3, 4, 5] ... function add(5) .... new_array (or maybe change the old array) = [6, 7, 8, 9, 10] .

Here is the question: 

// write code so that console logs print out true
//   add(addValue) should return a new arrays where addValue
//   is added to each value of original array
//   i.e. [6, 7, 8, 9, 10] > 

var e = [1, 2, 3, 4, 5];
console.log(e.add(5) == '[6,7,8,9,10]');

this gives me my result but this is not the question

var e = [1, 2, 3, 4, 5];
var addValue = (e, Val) => e.map(add=>add+Val);

console.log(addValue(e,5));

Upvotes: 0

Views: 90

Answers (3)

Patrick Roberts
Patrick Roberts

Reputation: 51926

The most straightforward way to do this would be to invoke Array#map() with a scoped function from within Array#add(), using the number argument passed in:

Array.prototype.add = function add (number) {
  return JSON.stringify(this.map(value => value + number))
}

var e = [1, 2, 3, 4, 5]

console.log(e.add(5) == '[6,7,8,9,10]')

The reason you must wrap in JSON.stringify() is because Array#toString() and Array#join() do not include the wrapping square brackets as in JSON encoding.

Upvotes: 1

prabushitha
prabushitha

Reputation: 1483

Use prototypes

Array.prototype.add = function(val) {
    for(var i=0;i<this.length;i++){
         this[i] = this[i]+val;
    }
};
e.add(6);
console.log(e);

Upvotes: 0

Andy
Andy

Reputation: 63550

Write a function that accepts the integer that you're going to add with, and returns a new function that will perform the addition calculation when you pass it an array:

function add(n) {
  return function (arr) {
    return arr.map(function (el) {
      return n + el;
    });
  }
}

const add5 = add(5);
add5([1, 2, 3, 4, 5]); // [6, 7, 8, 9, 10]

DEMO

You don't even need to create a new variable to hold the returned function:

add(5)([1, 2, 3, 4, 5]);

In an ES6 one-liner:

const add = (n) => (arr) => arr.map(el => n + el);

DEMO

And if you really wanted to add it to the Array.prototype (making sure you check that the new method you're proposing isn't already on the the prototype):

if (!(Array.prototype.add)) {
  Array.prototype.add = function (n) {
    return this.map(function (el) {
      return n + el;
     });
  }
}

[1, 2, 3, 4, 5].add(5); // [6, 7, 8, 9, 10]

DEMO

Upvotes: 2

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