convert String into integer in java script without using any built in functions

Question

Is there any trick to convert string to integer in javascript without using any function and methods?

var s = "5"
console.log(typeof(s)) // out put is string 
console.log(typeof(parseInt(s))) // i want out put which is number with out using parseInt() or other functions for optimizing code.

Any help would be appreciated. Thanks in advance.

my question is different first read full question i know this type of question was asked before — code7004, Feb 28 '19 at 07:17
Possible duplicate: https://stackoverflow.com/questions/1133770/convert-a-string-to-an-integer-in-javascript. — Rajesh, Feb 28 '19 at 07:21
there is an oneother answer with using (-) which cast string in to integer — manan5439, Feb 28 '19 at 07:26
@Rajesh Please don't stuck to the example code, the question says "_convert string to integer_" Any string ... — Teemu, Feb 28 '19 at 07:27
@Teemu So for `s="5.5"`, expected output should be `5` and not `5.5` as `+s` returns... Damn! I didn't think of this — Rajesh, Feb 28 '19 at 07:30

score 6 · Answer 1 · edited Mar 04 '19 at 12:17

6

You can cast the string to number using unary plus (+). This will do nothing much beside some code optimization.

var s = "5"
s = +s;
console.log(typeof(s), s);

var s = "5.5"
s = +s;
console.log(typeof(s), s);

edited Mar 04 '19 at 12:17

Takit Isy

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answered Feb 28 '19 at 07:11

Mamun

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`var s = "5.5"` What now? – Teemu Feb 28 '19 at 07:21
1

@TakitIsy Exactly, and that's not what was asked ("_convert string to __integer___"). It doesn't matter, though, since OP has accepted an answer which doesn't do what they actually asked for ... – Teemu Mar 04 '19 at 13:47
@Teemu I agree, but well… I guess the OP meant *number* and not *integer* anyway. For many, *integers* are just *numbers*. – Takit Isy Mar 04 '19 at 14:57

manan5439 · Accepted Answer · 2021-02-25T22:06:51.663

5

here is a most effective way to convert string into int without using any built in function have a look at code. Thank you:)

var s = "5"
var i = s - 0
console.log(typeof(i)) // you will get a number without using any built in function... because (-) will cast string in to number

edited Feb 25 '21 at 22:06

answered Feb 28 '19 at 07:15

manan5439

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I find much more in this explanation. – code7004 Feb 28 '19 at 14:26

Rajesh · Answer 3 · 2019-02-28T07:32:06.093

3

You can try using bit-wise operator s|0. This will convert value to integer. However, this will also convert floating values to integer.

var s = "5"
var y = s|0;
console.log(typeof(y), s, y);

var s = "5.5"
var y = s|0;
console.log(typeof(y), s, y);

edited Feb 28 '19 at 07:32

answered Feb 28 '19 at 07:24

Rajesh

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score 0 · Answer 4 · answered Oct 06 '22 at 22:10

Basically if you are searching "whole logic" to convert string to int then you have to find ASCII code for each alphabet in string and then convert it to integer and make sum of all 48 to 57 are ASCII codes are for number 0 to 1. Below is example code

let parseINT = (b) => b.split("").map((e,i) => {
    let value = e.charCodeAt(0) - 48;
    return value * [...Array(((i - b.length) * -1)).keys()].reduce((a, b) => a > 0 ? (a * 10) : 1, 0);
}).reduce((a, b) => a + b, 0)

or short form will be like

let parseINT = (b) => b.split("").map((e,i) => ((e.charCodeAt(0)  <= 57 ? e.charCodeAt(0) : 48) - 48) * [...Array(((i - b.length) * -1)).keys()].reduce((a, b) => a > 0 ? (a * 10) : 1, 0)).reduce((a, b) => a + b, 0);

convert String into integer in java script without using any built in functions

4 Answers4