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JavaScript JavaScript Basics (Retired) Making Decisions with Conditional Statements Review Conditional Statements and Comparison Operators

!== and != whats the difference

I know that != not equal to !== strict not equal to but I'm having problems trying to apply this concept

1 Answer

Steven Parker
Steven Parker
217,419 Points

The difference has to do with the JavaScript mechanism called "type coercion". That means if you compare things of different types, the system will try to convert one of them to the other's type (if possible) before comparing them. So the "strictly" versions will consider two things to not match if they are different types, no matter what the value, but the normal comparison will be based on the values of the items.

Here's a little demo:

var neq  = 0 !=  false ? "is NOT" : "is";
var sneq = 0 !== false ? "is NOT" : "is";
document.write("Zero " + neq + " equal to <i>false</i>, but<br>");
document.write("zero " + sneq + " <u>strictly</u> equal to <i>false</i>.");

Zero is equal to false, but
zero is NOT strictly equal to false.