CODEWITHSUNDEEP
javascript
LED Fantom
LED Fantom

Reputation: 1373

'undefined' is returned after comparing numbers with a var set to POSITIVE_INFINITY and MAX_VALUE in javascript

Description: I am working on some exercises to get familiar with Javascript. One of the question asks me to find the smallest number in a given object below.

var myObj = { key: [5, 8, 1, 4] };

I set my initial value of smallest to POSITIVE_INFINITY and MAX_VALUE. After I ran my program (see below), undefined was returned. However, when I set smallest to 99999, the program is executed correctly.

My Question: What causes undefined returned when I set my variable, smallest, to POSITIVE_INFINITY and MAX_VALUE ? Thank you in advance for your help. 

var myObj = { key: [5, 8, 1, 4] };

function getSmallest(obj, key) {

  //var smallest = Math.POSITIVE_INFINITY;  //---> undefined is returned
  //var smallest = Math.MAX_VALUE;  //--->undefined is returned
  var smallest = 99999;  //---> Correct result is returned

  if (!obj.hasOwnProperty(key) || !Array.isArray(obj[key]) || obj[key].length === 0) {
    return undefined;
  }

  for (var i in obj[key]) {
    if (obj[key][i] < smallest) {
      smallest = obj[key][i];
    }
  }

  return smallest;
}

var output = getSmallest(myObj, 'key');
console.log(output);

Upvotes: 0

Views: 113

Answers (4)

clabe45
clabe45

Reputation: 2454

There is no MAX_INFINITY constant in JavaScript. Even POSITIVE_INFINITY would not fulfill the task correctly, because that is greater than MAX_VALUE. However, you could simply use Math.min.apply as mentioned in the comments.

If you really want to understand the logic behind JavaScript number constants, you could use NEGATIVE_INFINITY, and see that it is less than all JavaScript numbers (including Number.MIN_SAFE_INTEGER):

Number.NEGATIVE_INFINITY < Number.MIN_SAFE_INTEGER   // true

Upvotes: 0

Pritam Banerjee
Pritam Banerjee

Reputation: 18933

Try this (use Number):

var max = Number.MAX_VALUE;
console.log(max);

var min = Number.MIN_VALUE;
console.log(min);

Upvotes: 0

DoNotDownvote_JustUpvote
DoNotDownvote_JustUpvote

Reputation: 77

Simply because it's Number.POSITIVE_INFINITY, not Math.POSITIVE_INFINITY. (Same for MAX_VALUE)

Upvotes: 0

Bergi
Bergi

Reputation: 664936

The MAX_VALUE and POSITIVE_INFINITY constants are properties of the Number object, not of Math. You can also use the global Infinity constant.

Upvotes: 2

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