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Vitor Oliveira
6,766 PointsDifference between == and ===
1) What's the difference between == and ===?
Could you show me two examples using if statement?
2) Why is undefined === null returns false and undefined == null returns true?
4 Answers
Jeff Jacobson-Swartfager
15,419 PointsThe difference is in how strict they are in comparing the equality of the values. MDN has a good reference on this.
== is less strict than ===. A good example of this is 1 vs "1":
1 == "1"
> true
1 === "1"
> false
1 is a number. "1" is a string. In the first comparison, it evaluates to true because it converts both values to the same type before doing the comparison. The second comparison is comparing the value type as well; since they are not the same type, they are not the same.
Vitor Oliveira
6,766 PointsThank you! It was very helpful.
Jeff Jacobson-Swartfager
15,419 PointsI'm glad I could help!
Dean McKenzie
11,149 PointsThanks Jeff nicely explained!
Ben H
1,114 Points== tests that the values are the same === tests that the values AND types are the same
Jeff Jacobson-Swartfager
15,419 PointsJeff Jacobson-Swartfager
15,419 PointsSimilarly,
undefined == nullreturnstruebecause the comparison converts the two values to the same type first.undefined === nullreturnsfalsebecause the comparison compares the value types, which are different.MDN on undefined. MDN on null.