How to convert a string to an integer in JavaScript

Question

How do I convert a string to an integer in JavaScript

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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   gt   string     var num1    12423    typeof num1   gt   number     num1    gt  12423

User · Answer

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   lt 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   lt 1    on Firefox is a little bit faster   lt 1    I update above picture and test

User · Answer

Summing the multiplication of digits with their respective power of ten   i e  123   100 20 3   1 100   2 10   3 1   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  lt  array length  i          let exp   array length- i 1       let value   array i    Math pow 10 exp       sum  value     return sum

User · Answer

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  quot 97 quot   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  quot 92px quot   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  quot 97 800 quot   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  quot 97 quot     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  quot 97 654 quot         other options are Math ceil  Math round var fixed   Number  quot 97 654 quot   toFixed 0      rounded rather than truncated var bitwised   Number  quot 97 654 quot   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     quot 3000000000 654 quot      -1294967296    This is the same as Number  quot 3000000000 654 quot   0  quot 3000000000 654 quot   gt  gt  gt  0     3000000000    unsigned right shift gives you an extra bit  quot 300000000000 654 quot   gt  gt  gt  0     3647256576    but still fails with larger numbers  To work correctly with larger numbers  you should use the rounding methods Math floor  quot 3000000000 654 quot       3000000000    This is the same as Math floor Number  quot 3000000000 654 quot     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

User · Answer

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

User · Answer

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

User · Answer

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 here  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   gt  gt  gt  0     4294967294  2 123   gt  gt  gt  0     2  -5   gt  gt  gt  0     4294967291  5   gt  gt  gt  0     5

User · Answer

This  probably  isn t the best solution for parsing an integer  but if you need to  quot extract quot  one  for example   quot 1a2b3c quot      123  quot 198some text2hello world 30 quot      198230         this would work  only for integers    x000D   x000D  var str    3a9b0c3d2e9f8g   function extractInteger str      var result   0    var factor   1    for  var i   str length  i  gt  0  i--        if   isNaN str i - 1            result    parseInt str i - 1     factor       factor    10              return result    console log extractInteger str   x000D   x000D   x000D   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   x000D   x000D  var str    3a9b0c3d2e9f8g   function extractInteger str      var result   0    var factor   1    for  var i   str length  i  gt  0  i--        if  isNaN str i - 1    return NaN     result    parseInt str i - 1     factor     factor    10        return result    console log extractInteger str   x000D   x000D   x000D

User · Answer

x000D   x000D  function doSth    x000D    var a   document getElementById  input   value  x000D    document getElementById  number   innerHTML   toNumber a    1  x000D    x000D  function toNumber str   x000D    return  str  x000D    x000D   lt input id  input  type  text  gt  x000D   lt input onclick  doSth    type  submit  gt  x000D   lt span id  number  gt  lt  span gt  x000D   x000D   x000D

User · Answer

I only added one plus    before string and that was solution     052254    52254   Hope it helps

User · Answer

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

User · Answer

Here is the easiest solution  let myNumber    123    0    More easy solution  let myNumber     123

User · Answer

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

User · Answer

ParseInt   and   are different  parseInt  10 3456      returns 10    10 3456     returns 10 3456

User · Answer

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        gt  integer   0      Example 2 - Valid value  let value    1230 42   let integer    parseInt value  10     0        gt  integer   1230      Example 3 - Invalid value  let value        gt    return 412    let integer    parseInt value  10     0        gt  integer   0

User · Answer

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

User · Answer

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

User · Answer

Try parseInt   var number   parseInt  10   10     number will have value of 10

User · Answer

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  gt   1  ret     the str charCodeAt 0   amp  0xff   lt  lt   0      if  len  gt   2  ret     the str charCodeAt 1   amp  0xff   lt  lt   8      if  len  gt   3  ret     the str charCodeAt 2   amp  0xff   lt  lt  16      if  len  gt   4  ret     the str charCodeAt 3   amp  0xff   lt  lt  24      return ret    function int2str the int        var tmp              the int  amp  0x000000ff   gt  gt   0           the int  amp  0x0000ff00   gt  gt   8           the int  amp  0x00ff0000   gt  gt  16           the int  amp  0xff000000   gt  gt  24            var ret           for  var i 0  i lt 4  i              if  tmp i     0              break          ret    String fromCharCode tmp i              return ret

User · Answer

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

User · Answer

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

User · Answer

Try str - 0 to convert string to number    gt  str    0   gt  str - 0   0  gt  str    123   gt  str - 0   123  gt  str    -12   gt  str - 0   -12  gt  str    asdf   gt  str - 0   NaN  gt  str    12 34   gt  str - 0   12 34   Here are two links to compare the performance of several ways to convert string to int  https   jsperf com number-vs-parseint-vs-plus  http   phrogz net js string to number html

User · Answer

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

User · Answer

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

[javascript] How to convert a string to an integer in JavaScript?

Examples related to javascript

Examples related to string

Examples related to integer

Examples related to data-conversion