How to turn NaN from parseInt into 0 for an empty string

Question

Is it possible somehow to return 0 instead of NaN when parsing values in JavaScript   In case of the empty string parseInt returns NaN   Is it possible to do something like that in JavaScript to check for NaN   var value   parseInt tbb     NaN   0   parseInt tbb    Or maybe there is another function or jQuery plugin which may do something similar

User · Answer

I created a 2 prototype to handle this for me, one for a number, and one for a String.

// This is a safety check to make sure the prototype is not already defined.
Function.prototype.method = function (name, func) {
    if (!this.prototype[name]) {
        this.prototype[name] = func;
        return this;
    }
};

// returns the int value or -1 by default if it fails
Number.method('tryParseInt', function (defaultValue) {
    return parseInt(this) == this ? parseInt(this) : (defaultValue === undefined ? -1 : defaultValue);
});

// returns the int value or -1 by default if it fails
String.method('tryParseInt', function (defaultValue) {
    return parseInt(this) == this ? parseInt(this) : (defaultValue === undefined ? -1 : defaultValue);
});

If you dont want to use the safety check, use

String.prototype.tryParseInt = function(){
    /*Method body here*/
};
Number.prototype.tryParseInt = function(){
     /*Method body here*/
};

Example usage:

var test = 1;
console.log(test.tryParseInt()); // returns 1

var test2 = '1';
console.log(test2.tryParseInt()); // returns 1

var test3 = '1a';
console.log(test3.tryParseInt()); // returns -1 as that is the default

var test4 = '1a';
console.log(test4.tryParseInt(0));// returns 0, the specified default value

User · Answer

var value   isNaN parseInt tbb     0   parseInt tbb

User · Answer

I was surprised to not see anyone mention using Number     Granted it will parse decimals if provided  so will act differently than parseInt    however it already assumes base 10 and will turn    or even       in to 0

User · Answer

For people who are not restricted to parseInt  you can use the bitwise OR operator  which implicitly calls ToInt32 to its operands    var value   s   0      NaN   0        gt  gt  0          0        gt  gt  0     5    0        gt  gt  5     33Ab    0     gt  gt  0     0x23    0     gt  gt  35    113   0        gt  gt  113    -12   0        gt  gt  -12    3 9   0        gt  gt  3   Note  ToInt32 is different from parseInt   i e  parseInt  33Ab       33

User · Answer

function ToInt x  x parseInt x  return isNaN x  0 x                                                          var x   ToInt          - gt   x 0     x   ToInt  abc     - gt   x 0     x   ToInt  0 1     - gt   x 0     x   ToInt  5 9     - gt   x 5     x   ToInt 5 9      - gt   x 5     x   ToInt 5        - gt   x 5

User · Answer

I had a similar problem  firefox v34  with simple strings like   var myInt   parseInt  b4      So I came up with a quick hack of   var intVal         val  replace    0-9  gi         And then got all stupid complicated to deal with floats   ints for non-simple stuff   var myval    12 34    function slowParseNumber val  asInt       var ret   Number        val  replace    0-9    gi             return asInt   Math floor ret    ret    var floatVal   slowParseNumber myval    var intVal   slowParseNumber myval  true   console log floatVal  intVal     It will return 0 for things like   var intVal   slowParseNumber  b       yeilds 0

User · Answer

You can also use the isNaN   function   var s      var num   isNaN parseInt s     0   parseInt s

User · Answer

You can have very clean code  i had similar problems and i solved it by using    var a  bcd     parseInt a

User · Answer

implicit cast var value   parseInt tbb 1      see original question  Explanation  for those who don t find it trivial  Multiplying by one  a method called  quot implicit cast quot   attempts to turn the unknown type operand into the primitive type  number   In particular  an empty string would become number 0  making it an eligible type for parseInt      A very good example was also given above by PirateApp  who suggested to prepend the   sign  forcing JavaScript to use the Number implicit cast  Aug  20 update  parseInt  quot 0 quot  expr   gives better results  in particular for parseInt  quot 0 quot   str

User · Answer

For other people looking for this solution  just use     without parseInt  it is the cleanest mode   var a    hello   var b     a    If NaN  it will return 0 instead      OBS  This solution apply only for integers

User · Answer

Why not override the function  In that case you can always be sure it returns 0 in case of NaN    function original        parseInt   function             return original apply window  arguments     0            parseInt     Now  anywhere in your code   parseInt         0

User · Answer

Also this way   why not write a function and call it where ever required   I m assuming it s the entry into the form fields to perform calculations   var Nanprocessor   function  entry        if entry   NaN             return 0        else           return entry            outputfield value   Nanprocessor x        where x is a value that is collected from a from field    i e say x  parseInt formfield1 value      what s wrong doing this

User · Answer

Here is a tryParseInt method that I am using  this takes the default value as second parameter so it can be anything you require   function tryParseInt str  defaultValue        return parseInt str     str   parseInt str    defaultValue     tryParseInt     0    0  tryParseInt  string   0    0  tryParseInt  558   0    558

User · Answer

var s        var num   parseInt s     0    When not used with boolean values  the logical OR      operator returns the first expression  parseInt s   if it can be evaluated to true  otherwise it returns the second expression  0   The return value of parseInt     is NaN  NaN evaluates to false  so num ends up being set to 0

User · Answer

Does the job a lot cleaner than parseInt in my opinion  Use the  operator  var s       console log  s    var s    1024   s 1024  s   0  s 0  s   -1  s -1  s   2 456  s 2 456  s       s 0  s    wtf   s NaN

User · Answer

an helper function which still allow to use the radix  function parseIntWithFallback s  fallback  radix        var parsed   parseInt s  radix       return isNaN parsed    fallback   parsed

User · Answer

The problem  Other answers don t take into account that 0 is falsy  and thus the following will be 20 instead of 0   const myNumber   parseInt  0      20     20   The solution  I propose a helper function  that solves most of the issues   function getNumber   value  defaultValue        const num   parseInt value  10     return isNaN num    defaultValue   num      The helper function will give the following results   getNumber   value   0   defaultValue  20        0 getNumber   value   2   defaultValue  20        2 getNumber   value   2 2   defaultValue  20        2 getNumber   value   any string   defaultValue  20        20 getNumber   value  undefined  defaultValue  20        20 getNumber   value  null  defaultValue  20        20 getNumber   value  NaN  defaultValue  20        20 getNumber   value  false  defaultValue  20        20 getNumber   value  true  defaultValue  20        20

User · Answer

Do a separate check for an empty string   as it is one specific case   and set it to zero in this case   You could appeand  0  to the start  but then you need to add a prefix to indicate that it is a decimal and not an octal number

[javascript] How to turn NaN from parseInt into 0 for an empty string?

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