What s the fastest way to convert String to Number in JavaScript

Question

Any number  it s number   String looks like a number  it s number   Everything else  it goes NaN    a    gt  NaN  1    gt  1 1   gt  1

User · Answer

A fast way to convert strings to an integer is to use a bitwise or, like so:

x | 0

While it depends on how it is implemented, in theory it should be relatively fast (at least as fast as +x) since it will first cast x to a number and then perform a very efficient or.

User · Answer

The fastest way is using -0   const num    12 34  - 0

User · Answer

Here  is simple way to do it     var num   Number str     in this example str is the variable that contains the string  You can tested and see how it works open  Google chrome developer tools  then go to the console and paste the following code  read the comments to understand better how the conversion is done       Here Im creating my variable as a string var str    258        here im printing the string variable  str console log   str         here Im using typeof   this tells me that the variable str is the type  string console log   The variable str is type      typeof str        here is where the conversion happens    Number will take the string in the parentesis and transform it to a variable num as type  number var num   Number str   console log   The variable num is type      typeof num

User · Answer

You can try using UnitOf  a measurement and data type conversion library we just officially released  UnitOf is super fast  small in size  and efficient at converting any data type without ever throwing an error or null undefined  Default values you define or UnitOf s defaults are returned when a conversion is unsuccessful     One liner examples UnitOf DataType  12 5   toFloat      12 5 of type Float is returned  0 would be returned if conversion failed  UnitOf DataType  Not A Num   toInt 10     10 of type Int is returned as the conversion failed     Or as a variable var unit   UnitOf DataType  12 5    unit toInt 5     12 5 of type Float is returned  5 would be returned if the conversion failed  unit toFloat 8      12 of type Int is returned  8 would be returned if the conversion failed

User · Answer

I find that num   1 is simple  clear  and works for integers and floats

User · Answer

There are 4 ways to do it as far as I know   Number x   parseInt x  10   parseFloat x    x    By this quick test I made  it actually depends on browsers   http   jsperf com best-of-string-to-number-conversion 2  Implicit marked the fastest on 3 browsers  but it makes the code hard to read    So choose whatever you feel like it

User · Answer

Prefix the string with the   operator   console log   a      NaN console log   1      1 console log  1     1

User · Answer

There are at least 5 ways to do this   If you want to convert to integers only  another fast  and short  way is the double-bitwise not  i e  using two tilde characters    e g     x   Reference  http   james padolsey com cool-stuff double-bitwise-not   The 5 common ways I know so far to convert a string to a number all have their differences  there are more bitwise operators that work  but they all give the same result as      This JSFiddle shows the different results you can expect in the debug console  http   jsfiddle net TrueBlueAussie j7x0q0e3 22   var values     123             undefined             not a number              123 45              1234 error              2147483648              4999999999                for  var i   0  i  lt  values length  i         var x   values i        console log x       console log   Number x        Number x        console log   parseInt x  10        parseInt x  10        console log   parseFloat x        parseFloat x        console log    x        x       console log     x         x       Debug console   123   Number x    123   parseInt x  10    123   parseFloat x    123    x   123     x   123 undefined   Number x    NaN   parseInt x  10    NaN   parseFloat x    NaN    x   NaN     x   0 null   Number x    0   parseInt x  10    NaN   parseFloat x    NaN    x   0     x   0  not a number    Number x    NaN   parseInt x  10    NaN   parseFloat x    NaN    x   NaN     x   0 123 45   Number x    123 45   parseInt x  10    123   parseFloat x    123 45    x   123 45     x   123 1234 error   Number x    NaN   parseInt x  10    1234   parseFloat x    1234    x   NaN     x   0 2147483648   Number x    2147483648   parseInt x  10    2147483648   parseFloat x    2147483648    x   2147483648     x   -2147483648 4999999999   Number x    4999999999   parseInt x  10    4999999999   parseFloat x    4999999999    x   4999999999     x   705032703   The   x version results in a number in  more  cases  where others often result in undefined  but it fails for invalid input  e g  it will return 0 if the string contains non-number characters after a valid number    Overflow  Please note  Integer overflow and or bit truncation can occur with     but not the other conversions  While it is unusual to be entering such large values  you need to be aware of this  Example updated to include much larger values   Some Perf tests indicate that the standard parseInt and parseFloat functions are actually the fastest options  presumably highly optimised by browsers  but it all depends on your requirement as all options are fast enough  http   jsperf com best-of-string-to-number-conversion 37  This all depends on how the perf tests are configured as some show parseInt parseFloat to be much slower    My theory is    Lies Darn lines Statistics JSPerf results

User · Answer

This is probably not that fast  but has the added benefit of making sure your number is at least a certain value  e g  0   or at most a certain value   Math max input  0     If you need to ensure a minimum value  usually you d do  var number   Number input   if  number  lt  0  number   0    Math max      0  saves you from writing two statements

[javascript] What's the fastest way to convert String to Number in JavaScript?

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