Iterate between specific range of number in a array [duplicate]

Question

I have an array with two elements [5, 50]. I want this array iterate as [5, 6, 7,......, 49, 50].

I try below code. But not working as my expectation.

function All(arr) {
  let newArry = [];
  for(let i = arr[0]; i < arr[1]; i++ ) {
    newArry[i] = newArry.push(i);
  }
  return newArry;
}

console.log(All([5, 50]));

There are only two elements in your array.... you don't have 45 elements in your array. Can you clarify what it is exactly that you want to do? Sounds like you just need a for loop. — Brad
– Brad, Commented Jul 21, 2019 at 6:13

frogatto · Accepted Answer · 2019-07-21 06:28:30Z

2

Do like this remove newArry[i] =

function All(arr) {
    let newArry = [];
    for(let i = arr[0]; i < arr[1]; i++ ) {
        newArry.push(i);
    }
    return newArry;
}    
console.log(All([5, 50]));

edited Jul 21, 2019 at 6:28

frogatto

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answered Jul 21, 2019 at 6:15

Rishab

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Comments

Jake · Accepted Answer · 2019-07-21 06:39:45Z

Get the two values you want to iterate between:

const [start, end] = [5, 50];

Create a new array of length difference between your two points:

Array(end - start + 1) // [undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined]

Since all the values will be undefined, create an iterator object using Array#keys: Array(end - start + 1).keys() // [object Array Iterator]
Spread that into an array:

[...Array(end - start + 1).keys()] // [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45]

Map over the values to create your new array:

[...Array(end - start + 1).keys()].map(i => i + start) // [5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50]

...which gives you something like this:

const range = (n, m) => [...Array(m - n + 1).keys()].map(i => i + n);

const [start, end] = [5, 50];

console.log(range(start, end)); // [5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50]

Or, to maintain the API of the function in your question, like this:

const All = (arr) => {
    const [n, m] = arr;
    return [...Array(m - n + 1).keys()].map(i => i + n);
}

console.log(All([5, 50])); // [5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50]

Almog Gabay · Accepted Answer · 2019-07-21 06:14:24Z

-1

The Array.prototype.push method mutates the original array, so reassigning doesn't make sense. Just do:

newArray.push(i);

answered Jul 21, 2019 at 6:14

Almog Gabay

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