JavaScript Comparison
Comparison Operators
Comparison operators are used to compare two values.
Comparison operators always return true or
false.
Given that x = 5, the table below explains the comparison operators:
| Operator | Description | Comparing | Returns | |
|---|---|---|---|---|
| == | 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 if...else chapter of this tutorial.
JavaScript String Comparison
All the comparison operators above can also be used on strings:
Note that strings are compared alphabetically:
Comparing Different Types
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".
Alphabetically 1 is less than 21.
To secure a proper result, variables should be converted to the proper type before comparison:
Example
age = Number(age);
if (isNaN(age)) {
voteable = "Input is not a number";
} else {
voteable = (age < 18) ? "Too young" : "Old enough";
}
Try it Yourself »
