How to convert a string to an integer in JavaScript?
JavascriptStringIntegerData ConversionJavascript Problem Overview
How do I convert a string to an integer in JavaScript?
Javascript Solutions
Solution 1 - Javascript
The simplest way would be to use the native Number
function:
var x = Number("1000")
If that doesn't work for you, then there are the parseInt, unary plus, parseFloat with floor, and Math.round methods.
parseInt:
var x = parseInt("1000", 10); // you want to use radix 10
// so you get a decimal number even with a leading 0 and an old browser ([IE8, Firefox 20, Chrome 22 and older][1])
unary plus if your string is already in the form of an integer:
var x = +"1000";
if your string is or might be a float and you want an integer:
var x = Math.floor("1000.01"); //floor automatically converts string to number
or, if you're going to be using Math.floor several times:
var floor = Math.floor;
var x = floor("1000.01");
If you're the type who forgets to put the radix in when you call parseInt, you can use parseFloat and round it however you like. Here I use floor.
var floor = Math.floor;
var x = floor(parseFloat("1000.01"));
Interestingly, Math.round (like Math.floor) will do a string to number conversion, so if you want the number rounded (or if you have an integer in the string), this is a great way, maybe my favorite:
var round = Math.round;
var x = round("1000"); //equivalent to round("1000",0)
Solution 2 - Javascript
Try parseInt function:
var number = parseInt("10");
But there is a problem. If you try to convert "010" using parseInt function, it detects as octal number, and will return number 8. So, you need to specify a radix (from 2 to 36). In this case base 10.
parseInt(string, radix)
Example:
var result = parseInt("010", 10) == 10; // Returns true
var result = parseInt("010") == 10; // Returns false
Note that parseInt
ignores bad data after parsing anything valid.
This guid will parse as 51:
var result = parseInt('51e3daf6-b521-446a-9f5b-a1bb4d8bac36', 10) == 51; // Returns true
Solution 3 - Javascript
There are two main ways to convert a string to a number in javascript. One way is to parse it and the other way is to change its type to a Number. All of the tricks in the other answers (e.g. unary plus) involve implicitly coercing the type of the string to a number. You can also do the same thing explicitly with the Number function.
Parsing
var parsed = parseInt("97", 10);
parseInt and parseFloat are the two functions used for parsing strings to numbers. Parsing will stop silently if it hits a character it doesn't recognise, which can be useful for parsing strings like "92px", but it's also somewhat dangerous, since it won't give you any kind of error on bad input, instead you'll get back NaN unless the string starts with a number. Whitespace at the beginning of the string is ignored. Here's an example of it doing something different to what you want, and giving no indication that anything went wrong:
var widgetsSold = parseInt("97,800", 10); // widgetsSold is now 97
It's good practice to always specify the radix as the second argument. In older browsers, if the string started with a 0, it would be interpreted as octal if the radix wasn't specified which took a lot of people by surprise. The behaviour for hexadecimal is triggered by having the string start with 0x if no radix is specified, e.g. 0xff
. The standard actually changed with ecmascript 5, so modern browsers no longer trigger octal when there's a leading 0 if no radix has been specified. parseInt understands radixes up to base 36, in which case both upper and lower case letters are treated as equivalent.
Changing the Type of a String to a Number
All of the other tricks mentioned above that don't use parseInt, involve implicitly coercing the string into a number. I prefer to do this explicitly,
var cast = Number("97");
This has different behavior to the parse methods (although it still ignores whitespace). It's more strict: if it doesn't understand the whole of the string than it returns NaN
, so you can't use it for strings like 97px
. Since you want a primitive number rather than a Number wrapper object, make sure you don't put new
in front of the Number function.
Obviously, converting to a Number gives you a value that might be a float rather than an integer, so if you want an integer, you need to modify it. There are a few ways of doing this:
var rounded = Math.floor(Number("97.654")); // other options are Math.ceil, Math.round
var fixed = Number("97.654").toFixed(0); // rounded rather than truncated
var bitwised = Number("97.654")|0; // do not use for large numbers
Any bitwise operator (here I've done a bitwise or, but you could also do double negation as in an earlier answer or a bitshift) will convert the value to a 32bit integer, and most of them will convert to a signed integer. Note that this will not do want you want for large integers. If the integer cannot be represented in 32bits, it will wrap.
~~"3000000000.654" === -1294967296
// This is the same as
Number("3000000000.654")|0
"3000000000.654" >>> 0 === 3000000000 // unsigned right shift gives you an extra bit
"300000000000.654" >>> 0 === 3647256576 // but still fails with larger numbers
To work correctly with larger numbers, you should use the rounding methods
Math.floor("3000000000.654") === 3000000000
// This is the same as
Math.floor(Number("3000000000.654"))
Bear in mind that coeercion understands exponential notation and Infinity, so 2e2
is 200
rather than NaN, while the parse methods don't.
Custom
It's unlikely that either of these methods do exactly what you want. For example, usually I would want an error thrown if parsing fails, and I don't need support for Infinity, exponentials or leading whitespace. Depending on your usecase, sometimes it makes sense to write a custom conversion function.
Always check that the output of Number or one of the parse methods is the sort of number you expect. You will almost certainly want to use isNaN
to make sure the number is not NaN (usually the only way you find out that the parse failed).
Solution 4 - Javascript
ParseInt() and + are different
parseInt("10.3456") // returns 10
+"10.3456" // returns 10.3456
Solution 5 - Javascript
Fastest
var x = "1000"*1;
Test
Here is little comparison of speed (Mac Os only)... :)
For chrome 'plus' and 'mul' are fastest (>700,000,00 op/sec), 'Math.floor' is slowest. For Firefox 'plus' is slowest (!) 'mul' is fastest (>900,000,000 op/sec). In Safari 'parseInt' is fastes, 'number' is slowest (but resulats are quite similar, >13,000,000 <31,000,000). So Safari for cast string to int is more than 10x slower than other browsers. So the winner is 'mul' :)
You can run it on your browser by this link https://jsperf.com/js-cast-str-to-number/1
Update
I also test var x = ~~"1000";
- on Chrome and Safari is a little bit slower than var x = "1000"*1
(<1%), on Firefox is a little bit faster (<1%). I update above picture and test
Solution 6 - Javascript
Try parseInt.
var number = parseInt("10", 10); //number will have value of 10.
Solution 7 - Javascript
Though an old question, but maybe this can be helpful to someone.
I use this way of converting string to int number
var str = "25"; // string
var number = str*1; // number
So, when multiplying by 1, the value does not change, but js automatically returns a number.
But as it is shown below, this should be used if you are sure that the str
is a number(or can be represented as a number), otherwise it will return NaN - not a number.
you can create simple function to use, e.g.
function toNumber(str) {
return str*1;
}
Solution 8 - Javascript
I posted the wrong answer here, sorry. fixed.
This is an old question, but I love this trick:
~~"2.123"; //2
~~"5"; //5
The double bitwise negative drops off anything after the decimal point AND converts it to a number format. I've been told it's slightly faster than calling functions and whatnot, but I'm not entirely convinced.
EDIT: Another method I just saw https://stackoverflow.com/questions/3081987/what-good-does-zero-fill-bit-shifting-by-0-do-a-0/3082073#3082073">here</a> (a question about the javascript >>> operator, which is a zero-fill right shift) which shows that shifting a number by 0 with this operator converts the number to a uint32 which is nice if you also want it unsigned. Again, this converts to an unsigned integer, which can lead to strange behaviors if you use a signed number.
"-2.123" >>> 0; // 4294967294
"2.123" >>> 0; // 2
"-5" >>> 0; // 4294967291
"5" >>> 0; // 5
Solution 9 - Javascript
Beware if you use parseInt to convert a float in scientific notation! For example:
parseInt("5.6e-14")
will result in
5
instead of
0
Solution 10 - Javascript
In Javascript, you can do the following:-
ParseInt
parseInt("10.5") //returns 10
Multiplying with 1
var s = "10";
s = s*1; //returns 10
Using Unary Operator (+)
var s = "10";
s = +s; //returns 10
Using Bitwise Operator
(Note: It starts to break after 2140000000
. Ex:- ~~"2150000000" = -2144967296
)
var s= "10.5";
s = ~~s; //returns 10
Using Math.floor() or Math.ceil()
var s = "10";
s = Math.floor(s) || Math.ceil(s); //returns 10
Solution 11 - Javascript
Please see the below example.It will help clear your doubt
Example Result
parseInt("4") 4
parseInt("5aaa") 5
parseInt("4.33333") 4
parseInt("aaa"); NaN (means "Not a Number")
by using parseint function It will only give op of integer present and not the string
Solution 12 - Javascript
Also as a side note: Mootools has the function toInt() which is used on any native string (or float (or integer)).
"2".toInt() // 2
"2px".toInt() // 2
2.toInt() // 2
Solution 13 - Javascript
To convert a String into Integer, I recommend using parseFloat and NOT parseInt. Here's why:
Using parseFloat:
parseFloat('2.34cms') //Output: 2.34
parseFloat('12.5') //Output: 12.5
parseFloat('012.3') //Output: 12.3
Using parseInt:
parseInt('2.34cms') //Output: 2
parseInt('12.5') //Output: 12
parseInt('012.3') //Output: 12
So if you have noticed parseInt discards the values after the decimals, whereas parseFloat lets you work with floating point numbers and hence more suitable if you want to retain the values after decimals. Use parseInt if and only if you are sure that you want the integer value.
Solution 14 - Javascript
we can use +(stringOfNumber)
instead of using parseInt(stringOfNumber)
Ex: +("21")
returns int of 21 like the parseInt("21")
.
we can use this unary "+" operator for parsing float too...
Solution 15 - Javascript
There are many ways in JavaScript to convert a string to a number value... All simple and handy, choose the way which one works for you:
var num = Number("999.5"); //999.5
var num = parseInt("999.5", 10); //999
var num = parseFloat("999.5"); //999.5
var num = +"999.5"; //999.5
Also any Math operation converts them to number, for example...
var num = "999.5" / 1; //999.5
var num = "999.5" * 1; //999.5
var num = "999.5" - 1 + 1; //999.5
var num = "999.5" - 0; //999.5
var num = Math.floor("999.5"); //999
var num = ~~"999.5"; //999
My prefer way is using +
sign, which is the elegant way to convert a string to number in JavaScript.
Solution 16 - Javascript
Try str - 0
to convert string
to number
.
> str = '0'
> str - 0
0
> str = '123'
> str - 0
123
> str = '-12'
> str - 0
-12
> str = 'asdf'
> str - 0
NaN
> str = '12.34'
> str - 0
12.34
Here are two links to compare the performance of several ways to convert string to int
Solution 17 - Javascript
Here is the easiest solution
let myNumber = "123" | 0;
More easy solution
let myNumber = +"123";
Solution 18 - Javascript
In my opinion, no answer covers all edge cases as parsing a float should result in an error.
function parseInteger(value) {
if(value === '') return NaN;
const number = Number(value);
return Number.isInteger(number) ? number : NaN;
}
parseInteger("4") // 4
parseInteger("5aaa") // NaN
parseInteger("4.33333") // NaN
parseInteger("aaa"); // NaN
Solution 19 - Javascript
Google gave me this answer as result, so...
I actually needed to "save" a string as an integer, for a binding between C and JavaScript, so I convert the string into a integer value:
/*
Examples:
int2str( str2int("test") ) == "test" // true
int2str( str2int("t€st") ) // "t¬st", because "€".charCodeAt(0) is 8364, will be AND'ed with 0xff
Limitations:
max 4 chars, so it fits into an integer
*/
function str2int(the_str) {
var ret = 0;
var len = the_str.length;
if (len >= 1) ret += (the_str.charCodeAt(0) & 0xff) << 0;
if (len >= 2) ret += (the_str.charCodeAt(1) & 0xff) << 8;
if (len >= 3) ret += (the_str.charCodeAt(2) & 0xff) << 16;
if (len >= 4) ret += (the_str.charCodeAt(3) & 0xff) << 24;
return ret;
}
function int2str(the_int) {
var tmp = [
(the_int & 0x000000ff) >> 0,
(the_int & 0x0000ff00) >> 8,
(the_int & 0x00ff0000) >> 16,
(the_int & 0xff000000) >> 24
];
var ret = "";
for (var i=0; i<4; i++) {
if (tmp[i] == 0)
break;
ret += String.fromCharCode(tmp[i]);
}
return ret;
}
Solution 20 - Javascript
The easiest way would be to use +
like this
const strTen = "10"
const numTen = +strTen // string to number conversion
console.log(typeof strTen) // string
console.log(typeof numTen) // number
Solution 21 - Javascript
function parseIntSmarter(str) {
// ParseInt is bad because it returns 22 for "22thisendsintext"
// Number() is returns NaN if it ends in non-numbers, but it returns 0 for empty or whitespace strings.
return isNaN(Number(str)) ? NaN : parseInt(str, 10);
}
Solution 22 - Javascript
You can use plus. For example:
var personAge = '24';
var personAge1 = (+personAge)
then you can see the new variable's type bytypeof personAge1
; which is number
.
Solution 23 - Javascript
Another option is to double XOR the value with itself:
var i = 12.34;
console.log('i = ' + i);
console.log('i ⊕ i ⊕ i = ' + (i ^ i ^ i));
This will output:
i = 12.34
i ⊕ i ⊕ i = 12
Solution 24 - Javascript
I only added one plus(+) before string and that was solution!
+"052254" //52254
Hope it helps ;)
Solution 25 - Javascript
Summing the multiplication of digits with their respective power of ten:
i.e: 123 = 100+20+3 = 1100 + 2+10 + 31 = 1*(10^2) + 2*(10^1) + 3*(10^0)
function atoi(array) {
// use exp as (length - i), other option would be to reverse the array.
// multiply a[i] * 10^(exp) and sum
let sum = 0;
for (let i = 0; i < array.length; i++) {
let exp = array.length-(i+1);
let value = array[i] * Math.pow(10,exp);
sum+=value;
}
return sum;
}
Solution 26 - Javascript
The safest way to ensure you get a valid integer:
let integer = (parseInt(value, 10) || 0);
Examples:
// Example 1 - Invalid value:
let value = null;
let integer = (parseInt(value, 10) || 0);
// => integer = 0
// Example 2 - Valid value:
let value = "1230.42";
let integer = (parseInt(value, 10) || 0);
// => integer = 1230
// Example 3 - Invalid value:
let value = () => { return 412 };
let integer = (parseInt(value, 10) || 0);
// => integer = 0
Solution 27 - Javascript
all of the above are correct. Please be sure before that this is a number in a string by doing "typeot x === 'number'" other wise it will return NaN
var num = "fsdfsdf242342";
typeof num => 'string';
var num1 = "12423";
typeof num1 => 'number';
+num1 = > 12423`
Solution 28 - Javascript
function doSth(){
var a = document.getElementById('input').value;
document.getElementById('number').innerHTML = toNumber(a) + 1;
}
function toNumber(str){
return +str;
}
<input id="input" type="text">
<input onclick="doSth()" type="submit">
<span id="number"></span>
Solution 29 - Javascript
I use this
String.prototype.toInt = function (returnval) {
var i = parseInt(this);
return isNaN(i) ? returnval !== undefined ? returnval : - 1 : i;
}
this way I always get an int back.
Solution 30 - Javascript
This (probably) isn't the best solution for parsing an integer, but if you need to "extract" one, for example:
"1a2b3c" === 123
"198some text2hello world!30" === 198230
// ...
this would work (only for integers):
var str = '3a9b0c3d2e9f8g'
function extractInteger(str) {
var result = 0;
var factor = 1
for (var i = str.length; i > 0; i--) {
if (!isNaN(str[i - 1])) {
result += parseInt(str[i - 1]) * factor
factor *= 10
}
}
return result
}
console.log(extractInteger(str))
Of course, this would also work for parsing an integer, but would be slower than other methods.
You could also parse integers with this method and return NaN
if the string isn't a number, but I don't see why you'd want to since this relies on parseInt
internally and parseInt
is probably faster.
var str = '3a9b0c3d2e9f8g'
function extractInteger(str) {
var result = 0;
var factor = 1
for (var i = str.length; i > 0; i--) {
if (isNaN(str[i - 1])) return NaN
result += parseInt(str[i - 1]) * factor
factor *= 10
}
return result
}
console.log(extractInteger(str))
Solution 31 - Javascript
// return 200.12
Number(" 200.12 ") // return 200.12
Number("200.12") // return 200
Number("200")
// return 200
parseInt(" 200.12 ") // return 200
parseInt("200.12") // return 200
parseInt("200") // return NaN
parseInt("Text information")
> It will return the first number
// return 200
parseFloat("200 400") // return 200
parseFloat("200") // return NaN
parseFloat("Text information") // return 200.10
parseFloat("200.10")
> round a number to the nearest integer