When you wish to inhibit implied typecasts. For example:
3 == '3'
is true, whereas this is not:
3 === '3'
Douglas Crockford recommends always using strict comparison.
Delan Azabani
2010-05-22 06:25:01
+2
A:
To be honest, I'm always a bit dubious when someone says "ALWAYS" do xxx. I can see situations where it is desiderable to compare a number to a string. Obviously you could manually cast the string to a number but if JS can do it for you why bother? :)
nico
2010-05-22 06:41:20
@nico, agree, there are cases where you simply don't need it, a common case is when you want to compare against `null` and `undefined` in one step, `if (foo == null)` does the job, or when using the `typeof` operator, you also don't need it because it will *always* return a string... `if (typeof foo == "undefined")` is enough...
CMS
2010-05-22 06:47:36
+8
A:
It is strict type equality operator. It not only checks whether two are equal in value but also of the same type.
Consider a situation when you compare numbers or strings:
if (4 === 4) // same value and type
{
// true
}
but
if (4 == "4") // same value and different type but == used
{
// true
}
and
if (4 === "4") // same value but different type
{
// false
}
This applies to objects as well as arrays.
So in above cases, you have to make sensible choice whether to use == or ===
It is good idea to use === when you are sure about the type as well
Sarfraz
2010-05-22 06:25:10
+1
A:
You use it to check if a variable's containing value and type is same as the compared one.
Abdel Olakara
2010-05-22 06:26:48