What is === in javascript? [duplicate] - javascript

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Closed 12 years ago.
Possible Duplicate:
Javascript === vs == : Does it matter which “equal” operator I use?
Looking into the answer of Chris Brandsma in Advanced JavaScript Interview Questions what is === in Javascript.
If possible please provide a simple example

=== is the strict equal operator. It only returns a Boolean True if both the operands are equal and of the same type. If a is 2, and b is 4,
a === 2 (True)
b === 4 (True)
a === '2' (False)
vs True for all of the following,
a == 2
a == "2"
2 == '2'

=== is 'strict equal operator'. It returns true if both the operands are equal AND are of same type.
a = 2
b = '2'
a == b //returns True
a === b //returns False
Take a look at this tutorial.

please refer Strict Equality Check..

Related

Chain equality operator in javascript [duplicate]

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Can I use chained comparison operator syntax? [duplicate]
(6 answers)
Why does (0 < 5 < 3) return true?
(14 answers)
Closed 1 year ago.
I have a question about how chain equality works in JavaScript.
For example in python if you have:
a, b = 1, 2
a == b == False //False
Because it converts to:
(a == b) and (b == False)
So, finally it is False.
But when I try this in js:
console.log(1==2==false) // true
I got "true". I don't know why and how it is worked in js.
could you please help me out?
Reading left to right:
1==2 is false
false==false is true
in the code 1 == 2 == false
we read it as 1 == 2 == false
so basically 1 == 2 is false
and fasle == false is true

Javascript OR (||) with ternary operator [duplicate]

This question already has answers here:
Precedence: Logical or vs. Ternary operator
(2 answers)
Closed 3 years ago.
payload = {type: 3}
const type = payload.type || state.active === "period" ? 1 : 2;
// type returns 1
I'm surprised by the return of type which is 1.. I was expecting it to be 3.. What happened here? What I want to really achieve is if the type index is not available then state.active === "period" ? 1 : 2 will be the basis of the value of type..
How to achieve this in a clean one line?
You need parentheses, because of the operator precedence.
const type = payload.type || (state.active === "period" ? 1 : 2);

Should I use == or === In Javascript? [duplicate]

This question already has answers here:
Which equals operator (== vs ===) should be used in JavaScript comparisons?
(48 answers)
Difference between == and === in JavaScript [duplicate]
(2 answers)
Closed 8 years ago.
I am learning Javascript with codecademy, and I was doing some comparisons, and for my code I did:
`console.log(1 == 2)`
and it returned False.
I also did:
`console.log(2*2 === 3)`
and that also returned False.
To check that I have not made a mistake, I did:
`console.log(1 == 1)`
and that returned True
The instructions tell me that === means equal to.
Are there any problems with using == instead of ===? And, which is better to use and why?
Thanks for any help you can give me!
Using == compares only the values, === compares the type of the variable also.
1 == 1 -> true
1 == "1" -> true
1 === 1 -> true
1 === "1" -> false, because 1 is an integer and "1" is a string.
You need === if you have to determine if a function returns 0 or false, as 0 == false is true but 0 === false is false.
It really depends on the situation. It's usually recommended to use === because in most cases that's the right choice.
== means Similar while
=== means Equal. Meaning it takes object type in consideration.
Example
'1' == 1 is true
1 == 1 is true
'1' === 1 is false
1 === 1 is true
When using == it doesn't matter if 1 is a Number or a String.
http://www.w3schools.com/js/js_comparisons.asp
== is equal to || x==8 equals false
=== is exactly equal to (value and type) || x==="5" false
meaning that 5==="5" false; and 5===5 true
After all, it depends on which type of comparison you want.

What is the difference between == and === in JavaScript? [duplicate]

This question already has answers here:
Closed 11 years ago.
Possible Duplicate:
Javascript === vs == : Does it matter which “equal” operator I use?
When would JavaScript == make more sense than ===?
What is the difference between below methods in comparing a string with undefined value.
var x;
if(x==undefined)
{
alert(x);
}
and
if(x===undefined)
{
alert(x);
}
Why should i prefer second method in this case.. Please let me know advantages..
== attempts to convert the values to the same type before testing if they're the same. "5" == 5
=== does not do this; it requires objects to be of the same type to be equal. "5" !== 5
In this case, the result is:
x == undefined will be true if x is undefined or null.
x === undefined will only be true if x is undefined.
You should prefer the first method if you'd like undefined and null to be treated equivalently. One common use of this is optional function arguments.
function greet(name, greeting) {
if (name == undefined) name = 'World';
if (greeting == undefined) greeting = 'Hello';
alert(greeting + ' ' + name);
}
greet(); // alerts "Hello World"
greet("Bob"); // alerts "Hello Bob"
greet(null, "Goodbye"); // alerts "Goodbye World"
suppose we have x=5,
== is equal to
x==8 is false
x==5 is true
=== is exactly equal to (value and type)
x===5 is true
x==="5" is false
Hope you understand this concept
=== checks for the same type as well. You'll understand with a few examples:
(1 == '1') //Returns true
Since == doesn't bother with types, that returns true. However, if you want strict type checking, you'd use === because that returns true only if the it's of the same type, and is the same value.
(1 === '1') //Returns false
(1 === 1) //Returns true
Two strings are strictly equal when they have the same sequence of characters, same length, and same characters in corresponding
positions.
Two numbers are strictly equal when they are numerically equal (have the same number value). NaN is not equal to anything,
including NaN. Positive and negative zeros are equal to one another.
Two Boolean operands are strictly equal if both are true or both are false.
Two objects are strictly equal if they refer to the same Object.
Null and Undefined types are == (but not ===).
Reference
== is just comparing the two values, and if they are of different types, type conversion is done
=== compares the values and well as their types - so no type conversion will be done here.

what is the difference between '!= 'and '!== ' [duplicate]

This question already has answers here:
Closed 11 years ago.
Possible Duplicates:
Is there a difference between !== and != in PHP?
Javascript === vs == : Does it matter which “equal” operator I use?
In some cases when checking for not equal, I saw using != and in some places i saw !==. Is there any difference in that?
Example:
var x = 10;
if (x != 10) {
//...
}
and
if (x !== 10) {
//...
}
== compares only the value and converts between types to find an equality, === compares the types as well.
== means equal
=== means identical
1 is equal to "1", but not identical, because 1 is an integer and "1" is a string.
They are different in terms of strictness of comparison. !== compares variable types in addition to values.
!== will also check the type (int, string, etc.) while != doesn't.
For more information, see the PHP comparison operator documentation.
The !== is strict not equal: Difference between == and === in JavaScript
The difference is that
== (and !=) compare only the value,
=== (and !==) compare the value and the type.
For example
"1" == 1 returns true
"1" === 1 returns false, because one is a string and the other is an integer
Hope this helps. Cheers

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