What are comparison operators in JavaScript?
In JavaScript, there are two types of comparison operators:
- Type-converting (or Abstract)
- Strict
1. Type-converting comparison
This category includes all of the commonly known comparison operators (e.g., less-than, greater-than, equal-to, etc.). These are known as type-converting because, in case of a comparison between operands of different types, one of the operands is first converted to the other type and then the comparison is made.
Example
function check(){
if(5 <= '5.01')
return true;
else
return false;
}
The function check(), in the code snippet above, will return true. This is because '5', which is a String, is converted into a Number before comparison. Therefore, we use the type-converting operators when the main thing to compare is the value, not the type, of the two operands.
function check (){if("100" > 20)return true;elsereturn false;}console.log(check());
When comparing two Objects, all relational operators, except for the == operator, use the valueOf() method to convert the Objects into a suitable value for comparison. The == operator will only return true when both the Objects are same; i.e., the reference variables point to the same JavaScript Object:
function compare1 (a, b){if(a == b)console.log(a.name + " and " + b.name + " are equal");elseconsole.log(a.name + " is not equal to " + b.name);}function compare2 (a, b){if(a <= b)console.log(a.name + " is less than or equal to " + b.name);elseconsole.log(a.name + " is greater than " + b.name);}function Person(i, n){this.id = i;this.name = n;}Person.prototype.valueOf = function(){return this.id;}p = new Person(5, 'p');q = new Person(5, 'q');r = q;s = new Person(10, 's');;compare1(p, q); // Prints 'p is not equal to q'.compare1(q, r); // Prints 'q and q are equal'.compare2(r, s); // Prints 'q is less than or equal to s'.
2. Strict comparison
In a strict comparison, true is returned if, and only if, both the operands have the same type and value; moreover, in the case of JavaScript Objects, both should refer to the same Object.
The most commonly used strict comparison operators are the strict equality === and inequality !== operators:
var compare1 = function(){if(5 == '5')return true;elsereturn false;}var compare2 = function(){if(5 === '5')return true;elsereturn false;}console.log(compare1()); // Type-convertingconsole.log(compare2()); // Strict
Equality Operators in JavaScript
In-equality Operators in JavaScript
