Possible Duplicate:
Why does “,,,” == Array(4) in Javascript?
In JavaScript why does
",,," == new Array(4)
It returns true in Chrome Developer Tools, and nodejs console.
Asked
Active
Viewed 442 times
1
-
2Kind of ironic that `[,,,] != new Array(4)` – panda-34 Jun 10 '12 at 18:31
-
a `==` comparisation will compare only values. So both sides are type casted to string. Try `===` comparisation – Imdad Jun 10 '12 at 18:33
4 Answers
5
console.log(new Array(4).toString()); // ",,,"
casted to string with above value making both equal.
",,," == ",,," // true
JS sees that on left hand is a string and on right hand side an array which is not good for comparison, it casts array to string and then does the comparison.
Notice that:
log(",,," === new Array(4));
would result in false since === checks not only for value but also type and types are different of course.
Sarfraz
- 367,681
- 72
- 526
- 573
2
Because the new Array(4) is being implicitly cast to a string, which will equal ",,," (four empty elements, comma separated).
Tim Pote
- 25,751
- 6
- 60
- 64
2
Because Array(4).toString() returns ",,," - 4 empty elements, so only the commas between them
Maxim Krizhanovsky
- 25,260
- 5
- 51
- 86
1
An array in String form produces a comma separated list of the elements, ie 1,2,3,4. If there are no elements in the Array, it will show up as ,,,.
(new Array(4)).toString() produces ,,,.
Note that new Array(4) === ",,," returns false.
Wex
- 15,188
- 10
- 59
- 102