This question already has answers here:
Difference between == and === in JavaScript [duplicate]
(2 answers)
Closed 6 years ago.
I am using java script to compare values
if (cellValue == "true" || cellValue == true)
Instead of doing this can i use the ===operator in java script ?
The difference between == and === is that the first one (double equals) does type coercion, which can lead to goofy results:
0 == false
true
0 === false
false
It is usually recommended to use === as that will provide more predictable results and evaluate the true types of the values you're comparing.
Related
This question already has answers here:
Which equals operator (== vs ===) should be used in JavaScript comparisons?
(48 answers)
Triple equal signs return false for arrays in javascript. why?
(4 answers)
Closed 4 years ago.
Console logging this.byPassViewState returns ["01"]
if i do this.byPassViewState === ['01'] it returns false
typeof(this.byPassViewState) retuns object
My question is why this.byPassViewState returns false ? it suppose to be true right ? please tell me what i'm doing wrong here
You cannot compare 2 array with just using == or === operators.
The easiest way to compare array is using JSON.stringify().
let byPassViewState = ["01"];
let compare = (JSON.stringify(byPassViewState) == JSON.stringify(["01"]) );
console.log(compare);
Please Reference : How to compare arrays in JavaScript?
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'm new to Java Script
What is the exact difference between (== Vs ===, != Vs !==, etc) in JavaScript?
Have read some articles and wanted to be more clear on this.
Thanks in advance.
The == operator means equality after type conversion
1 == '1'; // true
1 == 1; // true
The === operator means equality without any conversion
1 === '1'; // false
1 === 1; // true
This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
JavaScript === vs == : Does it matter which “equal” operator I use?
Javascript operator !==
What's the difference between != and !==?
Can you give me an example where using != gives another result than using !==?
alert(1 != true);
alert(1 !== true);
The first one is false, the second true.
!= accept 1 as equals of true, null as equals of false and some others (because the values are automatically casted when being compared).
!== accept only "real" equalities (i.e. compares both the value and the type).
Example
This question already has answers here:
Closed 11 years ago.
Possible Duplicates:
Difference between == and === in JavaScript
Javascript === vs == : Does it matter which “equal” operator I use?
What's the difference between == and ===? Also between !== and !==?
There are lots of answers to this question on Stackoverflow already.
Short:
== only compares values
=== compares values + type
var check1 = '10',
check2 = 10;
check1 == check2 // true
check1 === check2 // false
"==" means equals, whereas "===" means identically equal.
In short, "==" will try and coerce/convert the types of values when doing a comparison, so "2"==2, whereas "===" will not.
This question already has answers here:
Closed 13 years ago.
Possible Duplicate:
Javascript === vs == : Does it matter which “equal” operator I use?
Why do I see lots of javascript code lately with expressions that look like this:
if(val === "something")
Why "===" instead of just "=="? What's the difference? When should I use one or the other?
The === does not allow type coercion, so something like this would return false:
if (2 === '2') // false
The "normal" javascript == operator does allow type coercion, and so this would return true:
if (2 == '2') // true
var a = 3;
var b = "3";
if (a == b) {
// this is true.
}
if (a === b) {
// this is false.
}
=== is typically referred to as the identity operator. Values being compared must be of the same type and value to be considered equal. == is typically referred to as the equality operator and performs type coercion to check equality.
An example
1 == '1' // returns true even though one is a number, the other a string
1 === '1' // returns false. different datatypes
Doug Crockford touches briefly on this in JavaScript the Good Parts google tech talk video. Worth spending an hour to watch.
Checks that the type as well as the values match. This is important since (0 == false) is true but (0 === false) is not true.