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
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)
Closed 5 years ago.
console.log(undefined !== null);//true
console.log(undefined == null);//true
I can't undestand why undefined !==null,but i know undefined == null,because The language specification explicitly says:
If x is null and y is undefined, return true
You're using strict equality for the first comparison and non-strict for the latter. You'll find that undefined === null is false as expected.
This question already has answers here:
Which equals operator (== vs ===) should be used in JavaScript comparisons?
(48 answers)
What's the reason to use === instead of == with typeof in Javascript?
(5 answers)
Closed 6 years ago.
Say I wanted a function that checked whether or not a variable is a string, the interwebs advised me as follows:
function is_string(s) { return typeof s === 'string'; }
but I can't think of any scenario where "typeof s" could return "string" without s actually being a string.
Is there any reason for that === operator instead of ==?
Reason being, I want to check types in a switch statement, AFAIK, the switch statement uses the loose comparison operator. Since I'm only looking for known types and don't need to check for undefined, it should be fine, right?
This question already has answers here:
Which equals operator (== vs ===) should be used in JavaScript comparisons?
(48 answers)
Closed 6 years ago.
Which of the following lines is correct?...
if (typeof value == 'boolean') { return value; }
... or ...
if (typeof value === 'boolean') { return value; }
I thought the double equal sign was a type of "soft compare" so the value variable could either be a string or formal type. Is this not so? I wonder because JSHint complained about the first version. I've changed it but now I'm worried that typeof won't return a string.
== is a soft compare, but typeof always returns a string.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/typeof
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.