How to use an Operator (+,-,x,/) to an Array using a for loop?

Question

You are given an array of five numbers called increaseByTwo. Use a for loop to iterate through the array and increase each number by two.

const increaseByTwo = [1,2,3,4,5];

I need the result to be [3,4,5,6,7]

I'm not sure how to add +2 to the array itself, or any operator.

I've currently tried

const increaseByTwo = [1,2,3,4,5];
for (let i=0, i<increaseByTwo.length, i++)
console.log (increaseByTwo + 2) 

Results turn out to be but 3 4 5 6 7

on each seperate line, but need it to do be on one [3,4,5,6,7]

• Taha Paksu: Results don't turn out to be like that.
• JuniorSQL: how do i modify my results to make it look nice as a list?
• Taha Paksu: in the console or in the browser? stackoverflow.com/questions/46141450/…
• adiga: Possible duplicate of With JavaScript how would I increment numbers in an array using a for loop?

Answer 1

var arr = [1,2,3,4,5];
console.log(arr.map((e)=> e + 2)) 

• varatharajan: @JuniorSQL go through this link. developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/…

Answer 2

const increaseByTwo = [1, 2, 3, 4, 5];
for (let i = 0; i < increaseByTwo.length; i++){ 
 increaseByTwo[i] = increaseByTwo[i] + 2; //increaseByTwo[i] += 2;
}
console.log(increaseByTwo);

Answer 3

You can simply use .map() to get the resultant array:

const input = [1,2,3,4,5];
const output = input.map(v => v += 2);
console.log(output);

Answer 4

You can always use the .map() operator to modify element values. For example,

let increaseByTwo = [1,2,3,4,5];
increaseByTwo = increaseByTwo.map(num=>num+2);
console.log(increaseByTwo);

Or, if you really want to use a for loop, you can use this:

let increaseByTwo = [1,2,3,4,5];
for(let i = 0;i<increaseByTwo.length;++i){
 increaseByTwo[i]+=2;
}
console.log(increaseByTwo);

This should both work.

Answer 5

MyArray.map((elt)=>(elt+2));

This will basically pass each element into the function

(elt) => elt + 2

and will apply the result to the element. You can also do

for(var i = 0; i < MyArray.length; i++) {
 MyArray[i] += 2;
}

Now, for multiple operations and numbers. If you have something like [1, 2, 3, 4, 5] and you want to do the following [1 + 4, 2 * 6, 3 - 4, 4 / 8, 5 + 6]

var operators = '+*-/+'.split('');
var secondnums = [4,6,4,8,6];
var MyArray = [1,2,3,4,5]; 
for(var i = 0; i < MyArray.length; i++) {
 MyArray[i] = eval(MyArray[i]+operators[i]+secondnums[i]);
}
console.log(MyArray)
// [5, 12, -1, 0.5, 11] AKA [1 + 4, 2 * 6, 3 - 4, 4 / 8, 5 + 6]