Javascript string integer comparisons

Question

I store some parameters client-side in HTML and then need to compare them as integers  Unfortunately I have come across a serious bug that I cannot explain  The bug seems to be that my JS reads parameters as strings rather than integers  causing my integer comparisons to fail   I have generated a small example of the error  which I also can t explain  The following returns  true  when run    javascript alert  2  gt  10

User · Answer

Parse the string into an integer using parseInt   javascript alert parseInt  2   10  gt parseInt  10   10

User · Answer

You can use Number   function also since it converts the object argument to a number that represents the object s value  Eg  javascript alert  Number  quot 2 quot    gt  Number  quot 10 quot

User · Answer

Checking that strings are integers is separate to comparing if one is greater or lesser than another  You should always compare number with number and string with string as the algorithm for dealing with mixed types not easy to remember    00100   lt   1     true   as they are both strings so only the first zero of  00100  is compared to  1  and because it s charCode is lower  it evaluates as lower   However    00100   lt  1    false   as the RHS is a number  the LHS is converted to number before the comparision   A simple integer check is   function isInt n      return     -   d    test n       It doesn t matter if n is a number or integer  it will be converted to a string before the test   If you really care about performance  then   var isInt    function       var re       -   d        return function n        return re test n               Noting that numbers like 1 0 will return false  If you want to count such numbers as integers too  then   var isInt    function       var re       -   d       var re2      0        return function n        return re test      n  replace re2                   Once that test is passed  converting to number for comparison can use a number of methods  I don t like parseInt   because it will truncate floats to make them look like ints  so all the following will be  equal    parseInt 2 9     parseInt  002  10     parseInt  2wewe     and so on   Once numbers are tested as integers  you can use the unary   operator to convert them to numbers in the comparision   if  isInt a   amp  amp  isInt b       if   a  lt   b           a and b are integers and a is less than b         Other methods are   Number a      liked by some because it s clear what is happening a   1         Not really obvious but it works  I don t like it

User · Answer

use parseInt and compare like below   javascript alert parseInt  2   gt parseInt  10

User · Answer

The alert   wants to display a string  so it will interpret  2   10  as a string   Use the following   var greater   parseInt  2    gt  parseInt  10    alert  Is greater than      greater    var less   parseInt  2    lt  parseInt  10    alert  Is less than      less

User · Answer

Comparing Numbers to String Equivalents Without Using parseInt  console log Number  2    gt  Number  10     console log    2  1   gt    10  1      var item     id  998    id    998   var isEqual    item id toString       id toString     isEqual

User · Answer

Always remember when we compare two strings  the comparison happens on chacracter basis  so  2     12  is true because the comparison will happen as  2     1  and in alphabetical way  2  is always greater than  1  as unicode  SO it will comeout true  I hope this helps

User · Answer

The answer is simple  Just divide string by 1  Examples    2   gt   10    - true   but   2  1  gt   10  1 - false   Also you can check if string value really is number    isNaN  1  1  - true  number   isNaN  1a  1  - false  string   isNaN  01  1  - true  number   isNaN   1  1  - true  number   isNaN   1abc  1  - false  string    But   isNaN    1  - true  but string    Solution  number         amp  amp   isNaN number 1

[javascript] Javascript string/integer comparisons

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