Javascript String to int conversion

Question

I have the following JS immbedded in a page   var round   Math round  var id     this  attr  id     var len   id length  var indexPos   len -1     index of the number so that we can split this up and used it as a title  var pasType   id substring 0  indexPos      adult  child or infant var ind   round id substring indexPos       converts the string index to an integer var number    id substring indexPos    1      creates the number that will go in the title window alert number     id will be something like adult0  and I need to take that string and split it into adult and 0 - this part works fine   The problem comes in when I try to increment the 0  As you can see I use Math round to convert it to an integer  and then add 1 to it - I expect 0 to be 1 after this  However  it doesn t seem to be converting it to integer  because I get 01  not 1  When testing this with adult1 the alert I get is 11   I m using this question for reference  and have also tried var number    id substring indexPos    which breaks the JS  unexpected identifier        Does anyone know what I m doing wrong  Is there a better way of doing this

User · Answer

This is to do with JavaScript s   in operator - if a number and a string are  added  up  the number is converted into a string   0   1    1  0    1      01    To solve this  use the   unary operator  or use parseInt       0    1     1 parseInt  0   10    1     1   The unary   operator converts it into a number  however if it s a decimal it will retain the decimal places   and parseInt   is self-explanatory  converts into number  ignoring decimal places    The second argument is necessary for parseInt   to use the correct base when leading 0s are placed   parseInt  010       8 in older browsers  10 in newer browsers parseInt  010   10      always 10 no matter what   There s also parseFloat   if you need to convert decimals in strings to their numeric value -   can do that too but it behaves slightly differently  that s another story though

User · Answer

JS will think that the 0 is a string  which it actually is  to convert it to a int  use the  parseInt   function  like   var numberAsInt   parseInt number  10        Second arg is radix  10 is decimal    If the number is not possible to convert to a int  it will return NaN  so I would recommend a check for that too in code used in production or at least if you are not 100  sure of the input

User · Answer

If you are sure id substring indexPos  is a number  you can do it like so   var number   Number id substring indexPos     1    Otherwise I suggest checking if the Number function evaluates correctly

User · Answer

Use parseInt     var number    parseInt id substring indexPos     1       creates the number that will go in the title

User · Answer

The parseInt   function parses a string and returns an integer 10 is the Radix or Base  DOC   var number   parseInt id substring indexPos    10     1

User · Answer

Convert by Number Class -  Eg    var n   Number  103    console log n 1    Output  104  Note - Number is class  When we pass string  then constructor of Number class will convert it

User · Answer

Although parseInt is the official function to do this  you can achieve the same with this code   number 1   The advantage is that you save some characters  which might save bandwidth if your code has to lots of such conversations

[javascript] Javascript String to int conversion

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