In JavaScript, is '!=' the same as '!=='? [duplicate]

This question already has answers here: Closed 12 years ago.

Possible Duplicates:开发者_StackOverflow中文版

Which equals operator (== vs ===) should be used in JavaScript comparisons?

What is the difference between != and !== operators in JavaScript?

Look at this commit:

Is != the same as !== in JavaScript?

---

They are subtly not the same.

!= checks the value
!== checks the value and type

'1' != 1   // false (these two are the same)
'1' !== 1 // true (these two are **not** the same).

In the previous example. The first half of the expression is a string, the second half is an integer.

---

From JavaScript syntax, Operators,

!== Not identical

!= Not equal

AND "Identical means equal and of same type."

From 5.4. Equality Operators:

"In JavaScript, numbers, strings, and boolean values are compared by value. ... On the other hand, objects, arrays, and functions are compared by reference. "

--

So in summary, are they the same? No, because there is an additional test with !== (over !=) for type sameness as well as equalness.

---

No, it is not the same. See for example here.

4 !== '4' returns true   (and 4 === '4' returns false)
4 != '4'  returns false  (and 4 == '4'  returns true)

---

The big difference is that != performs type coercion. That is, one value is effectively cast to the other before equality is checked. This is why, as in Amadiere's answer:

'1' != 1

evaluates to false. The same holds true for == v. ===. In general, avoid == and != unless you specifically want coercion to be performed. Use === and !== and check for exactly the result you're looking for.

---

It checks not only value, but also the type of the things compared.

This is also the same in PHP and some other languages too.