How to convert all elements in an array to integer in JavaScript?

Question

I am getting an array after some manipulation. I need to convert all array values as integers.

My sample code

var result_string = 'a,b,c,d|1,2,3,4';
result = result_string.split("|");
alpha = result[0];
count = result[1];
// console.log(alpha);
// console.log(count);
count_array = count.split(",");

count_array now contains 1,2,3,4 but I need these value to be in integers.

I had used parseInt(count_array);, but it fails. JS considers each value in this array as string.

Answer 1

ECMAScript5 provides a map method for Arrays, applying a function to all elements of an array. Here is an example:

var a = ['1','2','3']
var result = a.map(function (x) { 
  return parseInt(x, 10); 
});

console.log(result);

See Array.prototype.map()

Answer 2

You can do

var arrayOfNumbers = arrayOfStrings.map(Number);

• MDN Array.prototype.map

For older browsers which do not support Array.map, you can use Underscore

var arrayOfNumbers = _.map(arrayOfStrings, Number);

Answer 3

Number() can convert a string to a number like this:

var arr = ["1", "2", "3"];
arr = arr.map(Number);
console.log(arr); // [1, 2, 3]

Answer 4

You need to loop through and parse/convert the elements in your array, like this:

var result_string = 'a,b,c,d|1,2,3,4',
    result = result_string.split("|"),
    alpha = result[0],
    count = result[1],
    count_array = count.split(",");
for(var i=0; i<count_array.length;i++) count_array[i] = +count_array[i];
//now count_array contains numbers

You can test it out here. If the +, is throwing, think of it as:

for(var i=0; i<count_array.length;i++) count_array[i] = parseInt(count_array[i], 10);

Answer 5

The point against parseInt-approach:

There's no need to use lambdas and/or give radix parameter to parseInt, just use parseFloat or Number instead.

---

Reasons:

1. It's working:

   var src = "1,2,5,4,3";
   var ids = src.split(',').map(parseFloat); // [1, 2, 5, 4, 3]
   
   var obj = {1: ..., 3: ..., 4: ..., 7: ...};
   var keys= Object.keys(obj); // ["1", "3", "4", "7"]
   var ids = keys.map(parseFloat); // [1, 3, 4, 7]
   
   var arr = ["1", 5, "7", 11];
   var ints= arr.map(parseFloat); // [1, 5, 7, 11]
   ints[1] === "5" // false
   ints[1] === 5   // true
   ints[2] === "7" // false
   ints[2] === 7   // true
   

2. It's shorter.

3. It's a tiny bit quickier and takes advantage of cache, when parseInt-approach - doesn't:

     // execution time measure function
     // keep it simple, yeah?
   > var f = (function (arr, c, n, m) {
         var i,t,m,s=n();
         for(i=0;i++<c;)t=arr.map(m);
         return n()-s
     }).bind(null, "2,4,6,8,0,9,7,5,3,1".split(','), 1000000, Date.now);
   
   > f(Number) // first launch, just warming-up cache
   > 3971 // nice =)
   
   > f(Number)
   > 3964 // still the same
   
   > f(function(e){return+e})
   > 5132 // yup, just little bit slower
   
   > f(function(e){return+e})
   > 5112 // second run... and ok.
   
   > f(parseFloat)
   > 3727 // little bit quicker than .map(Number)
   
   > f(parseFloat)
   > 3737 // all ok
   
   > f(function(e){return parseInt(e,10)})
   > 21852 // awww, how adorable...
   
   > f(function(e){return parseInt(e)})
   > 22928 // maybe, without '10'?.. nope.
   
   > f(function(e){return parseInt(e)})
   > 22769 // second run... and nothing changes.
   
   > f(Number)
   > 3873 // and again
   > f(parseFloat)
   > 3583 // and again
   > f(function(e){return+e})
   > 4967 // and again
   
   > f(function(e){return parseInt(e,10)})
   > 21649 // dammit 'parseInt'! >_<
   

Notice: In Firefox parseInt works about 4 times faster, but still slower than others. In total: +e < Number < parseFloat < parseInt

Answer 6

Just loop the array and convert items:

for(var i=0, len=count_array.length; i<len; i++){
    count_array[i] = parseInt(count_array[i], 10);
}

Don't forget the second argument for parseInt.

Answer 7

If you want to convert an Array of digits to a single number just use:

Number(arrayOfDigits.join(''));

Example

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

const singleNumber = Number(arrayOfDigits.join(''));

console.log(singleNumber); //12345

Answer 8

var inp=readLine();//reading the input as one line string
var nums=inp.split(" ").map(Number);//making an array of numbers
console.log(nums);`

input : 1 9 0 65 5 7 output:[ 1, 9, 0, 65, 5, 7 ]

what if we dont use .map(Number)

code

var inp=readLine();//reading the input as one line string
var nums=inp.split(" ");//making an array of strings
console.log(nums);

input : 1 9 0 65 5 7 output:[ '1', '9', '0', '65', '5', '7']

Answer 9

const arrString = ["1","2","3","4","5"];
const arrInteger = arrString.map(x => Number.parseInt(x, 10));

Above one should be simple enough,

One tricky part is when you try to use point free function for map as below

const arrString = ["1","2","3","4","5"];
const arrInteger = arrString.map(Number.parseInt);

In this case, result will be [1, NaN, NaN, NaN, NaN] since function argument signature for map and parseInt differs

map expects - (value, index, array) where as parseInt expects - (value, radix)

Answer 10

How about this:

let x = [1,2,3,4,5]
let num = +x.join("")

Answer 11

Using jQuery, you can like the map() method like so;

 $.map(arr, function(val,i) { 
     return parseInt(val); 
 });

Answer 12

use "join()"

let digits =[1,2,3,4]
let number =digits.join("")
console.log(number)

the '("")'- is used to indicate the separator,if you use 'digits.join("a")', it will give : 1a2a3a4

Answer 13

To convert array of Integer to a Integer value you can use reduce() method of Javascript. Below is the example :

    const arrayOfDigits = [1, 2, 3, 4, 5];
    const int = arrayOfDigits.reduce((val, digit) => (val * 10) + digit, 0);
    console.log('Array to Integer : '+int); //12345
    console.log('Add to Integer : '+(int+1)); //123456

Answer 14

The simplest way to do this is to convert the array into string and then parse it as integer:

var result_string = 'a,b,c,d|1,2,3,4';
result = result_string.split("|");
alpha = result[0];
count = result[1];
console.log(alpha);
console.log(count);
count_array = parseInt(count.split(",").join(''));
console.log(count_array);