HTML tutorial
CSS3 tutorial
Bootstrap tutorial
JavaScript tutorial
JQuery tutorial
AngularJS tutorial
React tutorial
NodeJS tutorial
PHP tutorial
Python tutorial
Python3 tutorial
Django tutorial
Linux tutorial
Docker tutorial
Ruby tutorial
Java tutorial
C tutorial
C ++ tutorial
Perl tutorial
JSP tutorial
Lua tutorial
Scala tutorial
Go tutorial
ASP.NET tutorial
C # tutorial
Comparison and Logical operators are used to test for true or false
Comparison operators are used in logical statements to determine equality or difference between variables or values.
Given that x = 5, the table below explains the comparison operators:
| Operator | Description | Comparing | Returns | Try it |
|---|---|---|---|---|
| == | equal to | x == 8 | false | Try it » |
| x == 5 | true | Try it » | ||
| x == "5" | true | Try it » | ||
| === | equal value and equal type | x === 5 | true | Try it » |
| x === "5" | false | Try it » | ||
| != | not equal | x != 8 | true | Try it » |
| !== | not equal value or not equal type | x !== 5 | false | Try it » |
| x !== "5" | true | Try it » | ||
| x !== 8 | true | Try it » | ||
| > | greater than | x > 8 | false | Try it » |
| < | less than | x < 8 | true | Try it » |
| >= | greater than or equal to | x >= 8 | false | Try it » |
| <= | less than or equal to | x <= 8 | true | Try it » |
Comparison operators can be used in conditional statements to compare values and take action depending on the result:
if (age < 18) text = "Too young to buy alcohol";
You will learn more about the use of conditional statements in the next chapter of this tutorial.
Logical operators are used to determine the logic between variables or values.
Given that x = 6 and y = 3, the table below explains the logical operators:
| Operator | Description | Example | Try it |
|---|---|---|---|
| && | and | (x < 10 && y > 1) is true | Try it » |
| || | or | (x == 5 || y == 5) is false | Try it » |
| ! | not | !(x == y) is true | Try it » |
JavaScript also contains a conditional operator that assigns a value to a variable based on some condition.
Syntax
Example
let voteable = (age < 18) ? "Too young":"Old enough";
If the variable age is a value below 18, the value of the variable voteable will be "Too young", otherwise the value of voteable will be "Old enough".
Comparing data of different types may give unexpected results.
When comparing a string with a number, JavaScript will convert the string to
a number when doing the comparison. An empty string converts to 0. A non-numeric
string converts to NaN which is always false.
| Case | Value | Try |
|---|---|---|
| 2 < 12 | true | Try it » |
| 2 < "12" | true | Try it » |
| 2 < "John" | false | Try it » |
| 2 > "John" | false | Try it » |
| 2 == "John" | false | Try it » |
| "2" < "12" | false | Try it » |
| "2" > "12" | true | Try it » |
| "2" == "12" | false | Try it » |
When comparing two strings, "2" will be greater than "12", because (alphabetically) 1 is less than 2.
To secure a proper result, variables should be converted to the proper type before comparison:
age = Number(age);
if (isNaN(age)) {
voteable = "Input is not a number";
} else {
voteable = (age < 18) ? "Too young" : "Old enough";
}
Choose the correct comparison operator to alert true, when x is greater than y.
x = 10; y = 5; alert(x y);