JS Comparisons

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:

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:

Example

let text1 = "A";

let text2 = "B";

let result = text1 < text2;

Note that strings are compared alphabetically:

Example

let text1 = "20";

let text2 = "5";

let result = text1 < text2;

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.

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";

}